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git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux
Pull arm64 fixes from Catalin Marinas:
"Fixes and cpucaps.h automatic generation:
- Generate cpucaps.h at build time rather than carrying lots of
#defines. Merged at -rc1 to avoid some conflicts during the merge
window.
- Initialise RGSR_EL1.SEED in __cpu_setup() as it may be left as 0
out of reset and the IRG instruction would not function as expected
if only the architected pseudorandom number generator is
implemented.
- Fix potential race condition in __sync_icache_dcache() where the
PG_dcache_clean page flag is set before the actual cache
maintenance.
- Fix header include in BTI kselftests"
* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
arm64: Fix race condition on PG_dcache_clean in __sync_icache_dcache()
arm64: tools: Add __ASM_CPUCAPS_H to the endif in cpucaps.h
arm64: mte: initialize RGSR_EL1.SEED in __cpu_setup
kselftest/arm64: Add missing stddef.h include to BTI tests
arm64: Generate cpucaps.h
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To ensure that instructions are observable in a new mapping, the arm64
set_pte_at() implementation cleans the D-cache and invalidates the
I-cache to the PoU. As an optimisation, this is only done on executable
mappings and the PG_dcache_clean page flag is set to avoid future cache
maintenance on the same page.
When two different processes map the same page (e.g. private executable
file or shared mapping) there's a potential race on checking and setting
PG_dcache_clean via set_pte_at() -> __sync_icache_dcache(). While on the
fault paths the page is locked (PG_locked), mprotect() does not take the
page lock. The result is that one process may see the PG_dcache_clean
flag set but the I/D cache maintenance not yet performed.
Avoid test_and_set_bit(PG_dcache_clean) in favour of separate test_bit()
and set_bit(). In the rare event of a race, the cache maintenance is
done twice.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: <stable@vger.kernel.org>
Cc: Will Deacon <will@kernel.org>
Cc: Steven Price <steven.price@arm.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210514095001.13236-1-catalin.marinas@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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Anshuman suggested this.
Suggested-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20210513151819.12526-1-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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Pull kvm fixes from Paolo Bonzini:
- Lots of bug fixes.
- Fix virtualization of RDPID
- Virtualization of DR6_BUS_LOCK, which on bare metal is new to this
release
- More nested virtualization migration fixes (nSVM and eVMCS)
- Fix for KVM guest hibernation
- Fix for warning in SEV-ES SRCU usage
- Block KVM from loading on AMD machines with 5-level page tables, due
to the APM not mentioning how host CR4.LA57 exactly impacts the
guest.
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (48 commits)
KVM: SVM: Move GHCB unmapping to fix RCU warning
KVM: SVM: Invert user pointer casting in SEV {en,de}crypt helpers
kvm: Cap halt polling at kvm->max_halt_poll_ns
tools/kvm_stat: Fix documentation typo
KVM: x86: Prevent deadlock against tk_core.seq
KVM: x86: Cancel pvclock_gtod_work on module removal
KVM: x86: Prevent KVM SVM from loading on kernels with 5-level paging
KVM: X86: Expose bus lock debug exception to guest
KVM: X86: Add support for the emulation of DR6_BUS_LOCK bit
KVM: PPC: Book3S HV: Fix conversion to gfn-based MMU notifier callbacks
KVM: x86: Hide RDTSCP and RDPID if MSR_TSC_AUX probing failed
KVM: x86: Tie Intel and AMD behavior for MSR_TSC_AUX to guest CPU model
KVM: x86: Move uret MSR slot management to common x86
KVM: x86: Export the number of uret MSRs to vendor modules
KVM: VMX: Disable loading of TSX_CTRL MSR the more conventional way
KVM: VMX: Use common x86's uret MSR list as the one true list
KVM: VMX: Use flag to indicate "active" uret MSRs instead of sorting list
KVM: VMX: Configure list of user return MSRs at module init
KVM: x86: Add support for RDPID without RDTSCP
KVM: SVM: Probe and load MSR_TSC_AUX regardless of RDTSCP support in host
...
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A valid implementation choice for the ChooseRandomNonExcludedTag()
pseudocode function used by IRG is to behave in the same way as with
GCR_EL1.RRND=0. This would mean that RGSR_EL1.SEED is used as an LFSR
which must have a non-zero value in order for IRG to properly produce
pseudorandom numbers. However, RGSR_EL1 is reset to an UNKNOWN value
on soft reset and thus may reset to 0. Therefore we must initialize
RGSR_EL1.SEED to a non-zero value in order to ensure that IRG behaves
as expected.
Signed-off-by: Peter Collingbourne <pcc@google.com>
Fixes: 3b714d24ef17 ("arm64: mte: CPU feature detection and initial sysreg configuration")
Cc: <stable@vger.kernel.org> # 5.10
Link: https://linux-review.googlesource.com/id/I2b089b6c7d6f17ee37e2f0db7df5ad5bcc04526c
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20210507185905.1745402-1-pcc@google.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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The arm64 code allocates an internal constant to every CPU feature it can
detect, distinct from the public hwcap numbers we use to expose some
features to userspace. Currently this is maintained manually which is an
irritating source of conflicts when working on new features, to avoid this
replace the header with a simple text file listing the names we've assigned
and sort it to minimise conflicts.
As part of doing this we also do the Kbuild hookup required to hook up
an arch tools directory and to generate header files in there.
This will result in a renumbering and reordering of the existing constants,
since they are all internal only the values should not be important. The
reordering will impact the order in which some steps in enumeration handle
features but the algorithm is not intended to depend on this and I haven't
seen any issues when testing. Due to the UAO cpucap having been removed in
the past we end up with ARM64_NCAPS being 1 smaller than it was before.
Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20210428121231.11219-1-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 perf fix from Borislav Petkov:
"Handle power-gating of AMD IOMMU perf counters properly when they are
used"
* tag 'perf_urgent_for_v5.13_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/events/amd/iommu: Fix invalid Perf result due to IOMMU PMC power-gating
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 fixes from Borislav Petkov:
"A bunch of things accumulated for x86 in the last two weeks:
- Fix guest vtime accounting so that ticks happening while the guest
is running can also be accounted to it. Along with a consolidation
to the guest-specific context tracking helpers.
- Provide for the host NMI handler running after a VMX VMEXIT to be
able to run on the kernel stack correctly.
- Initialize MSR_TSC_AUX when RDPID is supported and not RDTSCP (virt
relevant - real hw supports both)
- A code generation improvement to TASK_SIZE_MAX through the use of
alternatives
- The usual misc and related cleanups and improvements"
* tag 'x86_urgent_for_v5.13_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
KVM: x86: Consolidate guest enter/exit logic to common helpers
context_tracking: KVM: Move guest enter/exit wrappers to KVM's domain
context_tracking: Consolidate guest enter/exit wrappers
sched/vtime: Move guest enter/exit vtime accounting to vtime.h
sched/vtime: Move vtime accounting external declarations above inlines
KVM: x86: Defer vtime accounting 'til after IRQ handling
context_tracking: Move guest exit vtime accounting to separate helpers
context_tracking: Move guest exit context tracking to separate helpers
KVM/VMX: Invoke NMI non-IST entry instead of IST entry
x86/cpu: Remove write_tsc() and write_rdtscp_aux() wrappers
x86/cpu: Initialize MSR_TSC_AUX if RDTSCP *or* RDPID is supported
x86/resctrl: Fix init const confusion
x86: Delete UD0, UD1 traces
x86/smpboot: Remove duplicate includes
x86/cpu: Use alternative to generate the TASK_SIZE_MAX constant
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git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux
Pull RISC-V fixes from Palmer Dabbelt:
- A fix to avoid over-allocating the kernel's mapping on !MMU systems,
which could lead to up to 2MiB of lost memory
- The SiFive address extension errata only manifest on rv64, they are
now disabled on rv32 where they are unnecessary
- A pair of late-landing cleanups
* tag 'riscv-for-linus-5.13-mw1' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux:
riscv: remove unused handle_exception symbol
riscv: Consistify protect_kernel_linear_mapping_text_rodata() use
riscv: enable SiFive errata CIP-453 and CIP-1200 Kconfig only if CONFIG_64BIT=y
riscv: Only extend kernel reservation if mapped read-only
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git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild
Pull more Kbuild updates from Masahiro Yamada:
- Convert sh and sparc to use generic shell scripts to generate the
syscall headers
- refactor .gitignore files
- Update kernel/config_data.gz only when the content of the .config
is really changed, which avoids the unneeded re-link of vmlinux
- move "remove stale files" workarounds to scripts/remove-stale-files
- suppress unused-but-set-variable warnings by default for Clang
as well
- fix locale setting LANG=C to LC_ALL=C
- improve 'make distclean'
- always keep intermediate objects from scripts/link-vmlinux.sh
- move IF_ENABLED out of <linux/kconfig.h> to make it self-contained
- misc cleanups
* tag 'kbuild-v5.13-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (25 commits)
linux/kconfig.h: replace IF_ENABLED() with PTR_IF() in <linux/kernel.h>
kbuild: Don't remove link-vmlinux temporary files on exit/signal
kbuild: remove the unneeded comments for external module builds
kbuild: make distclean remove tag files in sub-directories
kbuild: make distclean work against $(objtree) instead of $(srctree)
kbuild: refactor modname-multi by using suffix-search
kbuild: refactor fdtoverlay rule
kbuild: parameterize the .o part of suffix-search
arch: use cross_compiling to check whether it is a cross build or not
kbuild: remove ARCH=sh64 support from top Makefile
.gitignore: prefix local generated files with a slash
kbuild: replace LANG=C with LC_ALL=C
Makefile: Move -Wno-unused-but-set-variable out of GCC only block
kbuild: add a script to remove stale generated files
kbuild: update config_data.gz only when the content of .config is changed
.gitignore: ignore only top-level modules.builtin
.gitignore: move tags and TAGS close to other tag files
kernel/.gitgnore: remove stale timeconst.h and hz.bc
usr/include: refactor .gitignore
genksyms: fix stale comment
...
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Merge master back into next, this allows us to resolve some conflicts in
arch/powerpc/Kconfig, and also re-sort the symbols under config PPC so
that they are in alphabetical order again.
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git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux
Pull more arm64 updates from Catalin Marinas:
"A mix of fixes and clean-ups that turned up too late for the first
pull request:
- Restore terminal stack frame records. Their previous removal caused
traces which cross secondary_start_kernel to terminate one entry
too late, with a spurious "0" entry.
- Fix boot warning with pseudo-NMI due to the way we manipulate the
PMR register.
- ACPI fixes: avoid corruption of interrupt mappings on watchdog
probe failure (GTDT), prevent unregistering of GIC SGIs.
- Force SPARSEMEM_VMEMMAP as the only memory model, it saves with
having to test all the other combinations.
- Documentation fixes and updates: tagged address ABI exceptions on
brk/mmap/mremap(), event stream frequency, update booting
requirements on the configuration of traps"
* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
arm64: kernel: Update the stale comment
arm64: Fix the documented event stream frequency
arm64: entry: always set GIC_PRIO_PSR_I_SET during entry
arm64: Explicitly document boot requirements for SVE
arm64: Explicitly require that FPSIMD instructions do not trap
arm64: Relax booting requirements for configuration of traps
arm64: cpufeatures: use min and max
arm64: stacktrace: restore terminal records
arm64/vdso: Discard .note.gnu.property sections in vDSO
arm64: doc: Add brk/mmap/mremap() to the Tagged Address ABI Exceptions
psci: Remove unneeded semicolon
ACPI: irq: Prevent unregistering of GIC SGIs
ACPI: GTDT: Don't corrupt interrupt mappings on watchdow probe failure
arm64: Show three registers per line
arm64: remove HAVE_DEBUG_BUGVERBOSE
arm64: alternative: simplify passing alt_region
arm64: Force SPARSEMEM_VMEMMAP as the only memory management model
arm64: vdso32: drop -no-integrated-as flag
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Pull io_uring fixes from Jens Axboe:
"Mostly fixes for merge window merged code. In detail:
- Error case memory leak fixes (Colin, Zqiang)
- Add the tools/io_uring/ to the list of maintained files (Lukas)
- Set of fixes for the modified buffer registration API (Pavel)
- Sanitize io thread setup on x86 (Stefan)
- Ensure we truncate transfer count for registered buffers (Thadeu)"
* tag 'io_uring-5.13-2021-05-07' of git://git.kernel.dk/linux-block:
x86/process: setup io_threads more like normal user space threads
MAINTAINERS: add io_uring tool to IO_URING
io_uring: truncate lengths larger than MAX_RW_COUNT on provide buffers
io_uring: Fix memory leak in io_sqe_buffers_register()
io_uring: Fix premature return from loop and memory leak
io_uring: fix unchecked error in switch_start()
io_uring: allow empty slots for reg buffers
io_uring: add more build check for uapi
io_uring: dont overlap internal and user req flags
io_uring: fix drain with rsrc CQEs
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When an SEV-ES guest is running, the GHCB is unmapped as part of the
vCPU run support. However, kvm_vcpu_unmap() triggers an RCU dereference
warning with CONFIG_PROVE_LOCKING=y because the SRCU lock is released
before invoking the vCPU run support.
Move the GHCB unmapping into the prepare_guest_switch callback, which is
invoked while still holding the SRCU lock, eliminating the RCU dereference
warning.
Fixes: 291bd20d5d88 ("KVM: SVM: Add initial support for a VMGEXIT VMEXIT")
Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Message-Id: <b2f9b79d15166f2c3e4375c0d9bc3268b7696455.1620332081.git.thomas.lendacky@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Invert the user pointer params for SEV's helpers for encrypting and
decrypting guest memory so that they take a pointer and cast to an
unsigned long as necessary, as opposed to doing the opposite. Tagging a
non-pointer as __user is confusing and weird since a cast of some form
needs to occur to actually access the user data. This also fixes Sparse
warnings triggered by directly consuming the unsigned longs, which are
"noderef" due to the __user tag.
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210506231542.2331138-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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syzbot reported a possible deadlock in pvclock_gtod_notify():
CPU 0 CPU 1
write_seqcount_begin(&tk_core.seq);
pvclock_gtod_notify() spin_lock(&pool->lock);
queue_work(..., &pvclock_gtod_work) ktime_get()
spin_lock(&pool->lock); do {
seq = read_seqcount_begin(tk_core.seq)
...
} while (read_seqcount_retry(&tk_core.seq, seq);
While this is unlikely to happen, it's possible.
Delegate queue_work() to irq_work() which postpones it until the
tk_core.seq write held region is left and interrupts are reenabled.
Fixes: 16e8d74d2da9 ("KVM: x86: notifier for clocksource changes")
Reported-by: syzbot+6beae4000559d41d80f8@syzkaller.appspotmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Message-Id: <87h7jgm1zy.ffs@nanos.tec.linutronix.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Nothing prevents the following:
pvclock_gtod_notify()
queue_work(system_long_wq, &pvclock_gtod_work);
...
remove_module(kvm);
...
work_queue_run()
pvclock_gtod_work() <- UAF
Ditto for any other operation on that workqueue list head which touches
pvclock_gtod_work after module removal.
Cancel the work in kvm_arch_exit() to prevent that.
Fixes: 16e8d74d2da9 ("KVM: x86: notifier for clocksource changes")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Message-Id: <87czu4onry.ffs@nanos.tec.linutronix.de>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Disallow loading KVM SVM if 5-level paging is supported. In theory, NPT
for L1 should simply work, but there unknowns with respect to how the
guest's MAXPHYADDR will be handled by hardware.
Nested NPT is more problematic, as running an L1 VMM that is using
2-level page tables requires stacking single-entry PDP and PML4 tables in
KVM's NPT for L2, as there are no equivalent entries in L1's NPT to
shadow. Barring hardware magic, for 5-level paging, KVM would need stack
another layer to handle PML5.
Opportunistically rename the lm_root pointer, which is used for the
aforementioned stacking when shadowing 2-level L1 NPT, to pml4_root to
call out that it's specifically for PML4.
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210505204221.1934471-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Bus lock debug exception is an ability to notify the kernel by an #DB
trap after the instruction acquires a bus lock and is executed when
CPL>0. This allows the kernel to enforce user application throttling or
mitigations.
Existence of bus lock debug exception is enumerated via
CPUID.(EAX=7,ECX=0).ECX[24]. Software can enable these exceptions by
setting bit 2 of the MSR_IA32_DEBUGCTL. Expose the CPUID to guest and
emulate the MSR handling when guest enables it.
Support for this feature was originally developed by Xiaoyao Li and
Chenyi Qiang, but code has since changed enough that this patch has
nothing in common with theirs, except for this commit message.
Co-developed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Chenyi Qiang <chenyi.qiang@intel.com>
Message-Id: <20210202090433.13441-4-chenyi.qiang@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Bus lock debug exception introduces a new bit DR6_BUS_LOCK (bit 11 of
DR6) to indicate that bus lock #DB exception is generated. The set/clear
of DR6_BUS_LOCK is similar to the DR6_RTM. The processor clears
DR6_BUS_LOCK when the exception is generated. For all other #DB, the
processor sets this bit to 1. Software #DB handler should set this bit
before returning to the interrupted task.
In VMM, to avoid breaking the CPUs without bus lock #DB exception
support, activate the DR6_BUS_LOCK conditionally in DR6_FIXED_1 bits.
When intercepting the #DB exception caused by bus locks, bit 11 of the
exit qualification is set to identify it. The VMM should emulate the
exception by clearing the bit 11 of the guest DR6.
Co-developed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Chenyi Qiang <chenyi.qiang@intel.com>
Message-Id: <20210202090433.13441-3-chenyi.qiang@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Commit b1c5356e873c ("KVM: PPC: Convert to the gfn-based MMU notifier
callbacks") causes unmap_gfn_range and age_gfn callbacks to only work
on the first gfn in the range. It also makes the aging callbacks call
into both radix and hash aging functions for radix guests. Fix this.
Add warnings for the single-gfn calls that have been converted to range
callbacks, in case they ever receieve ranges greater than 1.
Fixes: b1c5356e873c ("KVM: PPC: Convert to the gfn-based MMU notifier callbacks")
Reported-by: Bharata B Rao <bharata@linux.ibm.com>
Tested-by: Bharata B Rao <bharata@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Message-Id: <20210505121509.1470207-1-npiggin@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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If probing MSR_TSC_AUX failed, hide RDTSCP and RDPID, and WARN if either
feature was reported as supported. In theory, such a scenario should
never happen as both Intel and AMD state that MSR_TSC_AUX is available if
RDTSCP or RDPID is supported. But, KVM injects #GP on MSR_TSC_AUX
accesses if probing failed, faults on WRMSR(MSR_TSC_AUX) may be fatal to
the guest (because they happen during early CPU bringup), and KVM itself
has effectively misreported RDPID support in the past.
Note, this also has the happy side effect of omitting MSR_TSC_AUX from
the list of MSRs that are exposed to userspace if probing the MSR fails.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-16-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Squish the Intel and AMD emulation of MSR_TSC_AUX together and tie it to
the guest CPU model instead of the host CPU behavior. While not strictly
necessary to avoid guest breakage, emulating cross-vendor "architecture"
will provide consistent behavior for the guest, e.g. WRMSR fault behavior
won't change if the vCPU is migrated to a host with divergent behavior.
Note, the "new" kvm_is_supported_user_return_msr() checks do not add new
functionality on either SVM or VMX. On SVM, the equivalent was
"tsc_aux_uret_slot < 0", and on VMX the check was buried in the
vmx_find_uret_msr() call at the find_uret_msr label.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-15-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Now that SVM and VMX both probe MSRs before "defining" user return slots
for them, consolidate the code for probe+define into common x86 and
eliminate the odd behavior of having the vendor code define the slot for
a given MSR.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-14-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Split out and export the number of configured user return MSRs so that
VMX can iterate over the set of MSRs without having to do its own tracking.
Keep the list itself internal to x86 so that vendor code still has to go
through the "official" APIs to add/modify entries.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-13-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Tag TSX_CTRL as not needing to be loaded when RTM isn't supported in the
host. Crushing the write mask to '0' has the same effect, but requires
more mental gymnastics to understand.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-12-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Drop VMX's global list of user return MSRs now that VMX doesn't resort said
list to isolate "active" MSRs, i.e. now that VMX's list and x86's list have
the same MSRs in the same order.
In addition to eliminating the redundant list, this will also allow moving
more of the list management into common x86.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-11-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Explicitly flag a uret MSR as needing to be loaded into hardware instead of
resorting the list of "active" MSRs and tracking how many MSRs in total
need to be loaded. The only benefit to sorting the list is that the loop
to load MSRs during vmx_prepare_switch_to_guest() doesn't need to iterate
over all supported uret MRS, only those that are active. But that is a
pointless optimization, as the most common case, running a 64-bit guest,
will load the vast majority of MSRs. Not to mention that a single WRMSR is
far more expensive than iterating over the list.
Providing a stable list order obviates the need to track a given MSR's
"slot" in the per-CPU list of user return MSRs; all lists simply use the
same ordering. Future patches will take advantage of the stable order to
further simplify the related code.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-10-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
Configure the list of user return MSRs that are actually supported at
module init instead of reprobing the list of possible MSRs every time a
vCPU is created. Curating the list on a per-vCPU basis is pointless; KVM
is completely hosed if the set of supported MSRs changes after module init,
or if the set of MSRs differs per physical PCU.
The per-vCPU lists also increase complexity (see __vmx_find_uret_msr()) and
creates corner cases that _should_ be impossible, but theoretically exist
in KVM, e.g. advertising RDTSCP to userspace without actually being able to
virtualize RDTSCP if probing MSR_TSC_AUX fails.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-9-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
Allow userspace to enable RDPID for a guest without also enabling RDTSCP.
Aside from checking for RDPID support in the obvious flows, VMX also needs
to set ENABLE_RDTSCP=1 when RDPID is exposed.
For the record, there is no known scenario where enabling RDPID without
RDTSCP is desirable. But, both AMD and Intel architectures allow for the
condition, i.e. this is purely to make KVM more architecturally accurate.
Fixes: 41cd02c6f7f6 ("kvm: x86: Expose RDPID in KVM_GET_SUPPORTED_CPUID")
Cc: stable@vger.kernel.org
Reported-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
Probe MSR_TSC_AUX whether or not RDTSCP is supported in the host, and
if probing succeeds, load the guest's MSR_TSC_AUX into hardware prior to
VMRUN. Because SVM doesn't support interception of RDPID, RDPID cannot
be disallowed in the guest (without resorting to binary translation).
Leaving the host's MSR_TSC_AUX in hardware would leak the host's value to
the guest if RDTSCP is not supported.
Note, there is also a kernel bug that prevents leaking the host's value.
The host kernel initializes MSR_TSC_AUX if and only if RDTSCP is
supported, even though the vDSO usage consumes MSR_TSC_AUX via RDPID.
I.e. if RDTSCP is not supported, there is no host value to leak. But,
if/when the host kernel bug is fixed, KVM would start leaking MSR_TSC_AUX
in the case where hardware supports RDPID but RDTSCP is unavailable for
whatever reason.
Probing MSR_TSC_AUX will also allow consolidating the probe and define
logic in common x86, and will make it simpler to condition the existence
of MSR_TSX_AUX (from the guest's perspective) on RDTSCP *or* RDPID.
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-7-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
Disable preemption when probing a user return MSR via RDSMR/WRMSR. If
the MSR holds a different value per logical CPU, the WRMSR could corrupt
the host's value if KVM is preempted between the RDMSR and WRMSR, and
then rescheduled on a different CPU.
Opportunistically land the helper in common x86, SVM will use the helper
in a future commit.
Fixes: 4be534102624 ("KVM: VMX: Initialize vmx->guest_msrs[] right after allocation")
Cc: stable@vger.kernel.org
Cc: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-6-seanjc@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
Add a dedicated intercept enum for RDPID instead of piggybacking RDTSCP.
Unlike VMX's ENABLE_RDTSCP, RDPID is not bound to SVM's RDTSCP intercept.
Fixes: fb6d4d340e05 ("KVM: x86: emulate RDPID")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-5-seanjc@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
Intercept RDTSCP to inject #UD if RDTSC is disabled in the guest.
Note, SVM does not support intercepting RDPID. Unlike VMX's
ENABLE_RDTSCP control, RDTSCP interception does not apply to RDPID. This
is a benign virtualization hole as the host kernel (incorrectly) sets
MSR_TSC_AUX if RDTSCP is supported, and KVM loads the guest's MSR_TSC_AUX
into hardware if RDTSCP is supported in the host, i.e. KVM will not leak
the host's MSR_TSC_AUX to the guest.
But, when the kernel bug is fixed, KVM will start leaking the host's
MSR_TSC_AUX if RDPID is supported in hardware, but RDTSCP isn't available
for whatever reason. This leak will be remedied in a future commit.
Fixes: 46896c73c1a4 ("KVM: svm: add support for RDTSCP")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-4-seanjc@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
Do not advertise emulation support for RDPID if RDTSCP is unsupported.
RDPID emulation subtly relies on MSR_TSC_AUX to exist in hardware, as
both vmx_get_msr() and svm_get_msr() will return an error if the MSR is
unsupported, i.e. ctxt->ops->get_msr() will fail and the emulator will
inject a #UD.
Note, RDPID emulation also relies on RDTSCP being enabled in the guest,
but this is a KVM bug and will eventually be fixed.
Fixes: fb6d4d340e05 ("KVM: x86: emulate RDPID")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-3-seanjc@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
Clear KVM's RDPID capability if the ENABLE_RDTSCP secondary exec control is
unsupported. Despite being enumerated in a separate CPUID flag, RDPID is
bundled under the same VMCS control as RDTSCP and will #UD in VMX non-root
if ENABLE_RDTSCP is not enabled.
Fixes: 41cd02c6f7f6 ("kvm: x86: Expose RDPID in KVM_GET_SUPPORTED_CPUID")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210504171734.1434054-2-seanjc@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
While in most cases, when returning to use the VMCB01,
the exit reason stored in it will be SVM_EXIT_VMRUN,
on first VM exit after a nested migration this field
can contain anything since the VM entry did happen
before the migration.
Remove this warning to avoid the false positive.
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210504143936.1644378-3-mlevitsk@redhat.com>
Fixes: 9a7de6ecc3ed ("KVM: nSVM: If VMRUN is single-stepped, queue the #DB intercept in nested_svm_vmexit()")
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
While usually the L1's GIF is set while L2 runs, and usually
migration nested state is loaded after a vCPU reset which
also sets L1's GIF to true, this is not guaranteed.
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210504143936.1644378-2-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
In ioctl KVM_X86_SET_MSR_FILTER, input from user space is validated
after a memdup_user(). For invalid inputs we'd memdup and then call
kfree unnecessarily. Hoist input validation to avoid kfree altogether.
Signed-off-by: Siddharth Chandrasekaran <sidcha@amazon.de>
Message-Id: <20210503122111.13775-1-sidcha@amazon.de>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
Eliminate the probably unwanted hole in 'struct kvm_vmx_nested_state_hdr':
Pre-patch:
struct kvm_vmx_nested_state_hdr {
__u64 vmxon_pa; /* 0 8 */
__u64 vmcs12_pa; /* 8 8 */
struct {
__u16 flags; /* 16 2 */
} smm; /* 16 2 */
/* XXX 2 bytes hole, try to pack */
__u32 flags; /* 20 4 */
__u64 preemption_timer_deadline; /* 24 8 */
};
Post-patch:
struct kvm_vmx_nested_state_hdr {
__u64 vmxon_pa; /* 0 8 */
__u64 vmcs12_pa; /* 8 8 */
struct {
__u16 flags; /* 16 2 */
} smm; /* 16 2 */
__u16 pad; /* 18 2 */
__u32 flags; /* 20 4 */
__u64 preemption_timer_deadline; /* 24 8 */
};
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210503150854.1144255-3-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
When enlightened VMCS is in use and nested state is migrated with
vmx_get_nested_state()/vmx_set_nested_state() KVM can't map evmcs
page right away: evmcs gpa is not 'struct kvm_vmx_nested_state_hdr'
and we can't read it from VP assist page because userspace may decide
to restore HV_X64_MSR_VP_ASSIST_PAGE after restoring nested state
(and QEMU, for example, does exactly that). To make sure eVMCS is
mapped /vmx_set_nested_state() raises KVM_REQ_GET_NESTED_STATE_PAGES
request.
Commit f2c7ef3ba955 ("KVM: nSVM: cancel KVM_REQ_GET_NESTED_STATE_PAGES
on nested vmexit") added KVM_REQ_GET_NESTED_STATE_PAGES clearing to
nested_vmx_vmexit() to make sure MSR permission bitmap is not switched
when an immediate exit from L2 to L1 happens right after migration (caused
by a pending event, for example). Unfortunately, in the exact same
situation we still need to have eVMCS mapped so
nested_sync_vmcs12_to_shadow() reflects changes in VMCS12 to eVMCS.
As a band-aid, restore nested_get_evmcs_page() when clearing
KVM_REQ_GET_NESTED_STATE_PAGES in nested_vmx_vmexit(). The 'fix' is far
from being ideal as we can't easily propagate possible failures and even if
we could, this is most likely already too late to do so. The whole
'KVM_REQ_GET_NESTED_STATE_PAGES' idea for mapping eVMCS after migration
seems to be fragile as we diverge too much from the 'native' path when
vmptr loading happens on vmx_set_nested_state().
Fixes: f2c7ef3ba955 ("KVM: nSVM: cancel KVM_REQ_GET_NESTED_STATE_PAGES on nested vmexit")
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210503150854.1144255-2-vkuznets@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
Simplify the code by making PV features shutdown happen in one place.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210414123544.1060604-6-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
Crash shutdown handler only disables kvmclock and steal time, other PV
features remain active so we risk corrupting memory or getting some
side-effects in kdump kernel. Move crash handler to kvm.c and unify
with CPU offline.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210414123544.1060604-5-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
Currenly, we disable kvmclock from machine_shutdown() hook and this
only happens for boot CPU. We need to disable it for all CPUs to
guard against memory corruption e.g. on restore from hibernate.
Note, writing '0' to kvmclock MSR doesn't clear memory location, it
just prevents hypervisor from updating the location so for the short
while after write and while CPU is still alive, the clock remains usable
and correct so we don't need to switch to some other clocksource.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210414123544.1060604-4-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
Various PV features (Async PF, PV EOI, steal time) work through memory
shared with hypervisor and when we restore from hibernation we must
properly teardown all these features to make sure hypervisor doesn't
write to stale locations after we jump to the previously hibernated kernel
(which can try to place anything there). For secondary CPUs the job is
already done by kvm_cpu_down_prepare(), register syscore ops to do
the same for boot CPU.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210414123544.1060604-3-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
|
|
Merge yet more updates from Andrew Morton:
"This is everything else from -mm for this merge window.
90 patches.
Subsystems affected by this patch series: mm (cleanups and slub),
alpha, procfs, sysctl, misc, core-kernel, bitmap, lib, compat,
checkpatch, epoll, isofs, nilfs2, hpfs, exit, fork, kexec, gcov,
panic, delayacct, gdb, resource, selftests, async, initramfs, ipc,
drivers/char, and spelling"
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (90 commits)
mm: fix typos in comments
mm: fix typos in comments
treewide: remove editor modelines and cruft
ipc/sem.c: spelling fix
fs: fat: fix spelling typo of values
kernel/sys.c: fix typo
kernel/up.c: fix typo
kernel/user_namespace.c: fix typos
kernel/umh.c: fix some spelling mistakes
include/linux/pgtable.h: few spelling fixes
mm/slab.c: fix spelling mistake "disired" -> "desired"
scripts/spelling.txt: add "overflw"
scripts/spelling.txt: Add "diabled" typo
scripts/spelling.txt: add "overlfow"
arm: print alloc free paths for address in registers
mm/vmalloc: remove vwrite()
mm: remove xlate_dev_kmem_ptr()
drivers/char: remove /dev/kmem for good
mm: fix some typos and code style problems
ipc/sem.c: mundane typo fixes
...
|
|
The section "19) Editor modelines and other cruft" in
Documentation/process/coding-style.rst clearly says, "Do not include any
of these in source files."
I recently receive a patch to explicitly add a new one.
Let's do treewide cleanups, otherwise some people follow the existing code
and attempt to upstream their favoriate editor setups.
It is even nicer if scripts/checkpatch.pl can check it.
If we like to impose coding style in an editor-independent manner, I think
editorconfig (patch [1]) is a saner solution.
[1] https://lore.kernel.org/lkml/20200703073143.423557-1-danny@kdrag0n.dev/
Link: https://lkml.kernel.org/r/20210324054457.1477489-1-masahiroy@kernel.org
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org> [auxdisplay]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
In case of a use after free kernel oops, the freeing path of the object
is required to debug futher. In most of cases the object address is
present in one of the registers.
Thus check the register's address and if it belongs to slab, print its
alloc and free path.
e.g. in the below issue register r6 belongs to slab, and a use after
free issue occurred on one of its dereferenced values:
Unable to handle kernel paging request at virtual address 6b6b6b6f
....
pc : [<c0538afc>] lr : [<c0465674>] psr: 60000013
sp : c8927d40 ip : ffffefff fp : c8aa8020
r10: c8927e10 r9 : 00000001 r8 : 00400cc0
r7 : 00000000 r6 : c8ab0180 r5 : c1804a80 r4 : c8aa8008
r3 : c1a5661c r2 : 00000000 r1 : 6b6b6b6b r0 : c139bf48
.....
Register r6 information: slab kmalloc-64 start c8ab0140 data offset 64 pointer offset 0 size 64 allocated at meminfo_proc_show+0x40/0x4fc
meminfo_proc_show+0x40/0x4fc
seq_read_iter+0x18c/0x4c4
proc_reg_read_iter+0x84/0xac
generic_file_splice_read+0xe8/0x17c
splice_direct_to_actor+0xb8/0x290
do_splice_direct+0xa0/0xe0
do_sendfile+0x2d0/0x438
sys_sendfile64+0x12c/0x140
ret_fast_syscall+0x0/0x58
0xbeeacde4
Free path:
meminfo_proc_show+0x5c/0x4fc
seq_read_iter+0x18c/0x4c4
proc_reg_read_iter+0x84/0xac
generic_file_splice_read+0xe8/0x17c
splice_direct_to_actor+0xb8/0x290
do_splice_direct+0xa0/0xe0
do_sendfile+0x2d0/0x438
sys_sendfile64+0x12c/0x140
ret_fast_syscall+0x0/0x58
0xbeeacde4
Link: https://lkml.kernel.org/r/1615891032-29160-3-git-send-email-maninder1.s@samsung.com
Co-developed-by: Vaneet Narang <v.narang@samsung.com>
Signed-off-by: Vaneet Narang <v.narang@samsung.com>
Signed-off-by: Maninder Singh <maninder1.s@samsung.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Since /dev/kmem has been removed, let's remove the xlate_dev_kmem_ptr()
leftovers.
Link: https://lkml.kernel.org/r/20210324102351.6932-3-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Brian Cain <bcain@codeaurora.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Palmer Dabbelt <palmerdabbelt@google.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Niklas Schnelle <schnelle@linux.ibm.com>
Cc: Pierre Morel <pmorel@linux.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Patch series "drivers/char: remove /dev/kmem for good".
Exploring /dev/kmem and /dev/mem in the context of memory hot(un)plug and
memory ballooning, I started questioning the existence of /dev/kmem.
Comparing it with the /proc/kcore implementation, it does not seem to be
able to deal with things like
a) Pages unmapped from the direct mapping (e.g., to be used by secretmem)
-> kern_addr_valid(). virt_addr_valid() is not sufficient.
b) Special cases like gart aperture memory that is not to be touched
-> mem_pfn_is_ram()
Unless I am missing something, it's at least broken in some cases and might
fault/crash the machine.
Looks like its existence has been questioned before in 2005 and 2010 [1],
after ~11 additional years, it might make sense to revive the discussion.
CONFIG_DEVKMEM is only enabled in a single defconfig (on purpose or by
mistake?). All distributions disable it: in Ubuntu it has been disabled
for more than 10 years, in Debian since 2.6.31, in Fedora at least
starting with FC3, in RHEL starting with RHEL4, in SUSE starting from
15sp2, and OpenSUSE has it disabled as well.
1) /dev/kmem was popular for rootkits [2] before it got disabled
basically everywhere. Ubuntu documents [3] "There is no modern user of
/dev/kmem any more beyond attackers using it to load kernel rootkits.".
RHEL documents in a BZ [5] "it served no practical purpose other than to
serve as a potential security problem or to enable binary module drivers
to access structures/functions they shouldn't be touching"
2) /proc/kcore is a decent interface to have a controlled way to read
kernel memory for debugging puposes. (will need some extensions to
deal with memory offlining/unplug, memory ballooning, and poisoned
pages, though)
3) It might be useful for corner case debugging [1]. KDB/KGDB might be a
better fit, especially, to write random memory; harder to shoot
yourself into the foot.
4) "Kernel Memory Editor" [4] hasn't seen any updates since 2000 and seems
to be incompatible with 64bit [1]. For educational purposes,
/proc/kcore might be used to monitor value updates -- or older
kernels can be used.
5) It's broken on arm64, and therefore, completely disabled there.
Looks like it's essentially unused and has been replaced by better
suited interfaces for individual tasks (/proc/kcore, KDB/KGDB). Let's
just remove it.
[1] https://lwn.net/Articles/147901/
[2] https://www.linuxjournal.com/article/10505
[3] https://wiki.ubuntu.com/Security/Features#A.2Fdev.2Fkmem_disabled
[4] https://sourceforge.net/projects/kme/
[5] https://bugzilla.redhat.com/show_bug.cgi?id=154796
Link: https://lkml.kernel.org/r/20210324102351.6932-1-david@redhat.com
Link: https://lkml.kernel.org/r/20210324102351.6932-2-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Alexander A. Klimov" <grandmaster@al2klimov.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Andrey Zhizhikin <andrey.zhizhikin@leica-geosystems.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Brian Cain <bcain@codeaurora.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Chris Zankel <chris@zankel.net>
Cc: Corentin Labbe <clabbe@baylibre.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Gregory Clement <gregory.clement@bootlin.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Hillf Danton <hdanton@sina.com>
Cc: huang ying <huang.ying.caritas@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: James Troup <james.troup@canonical.com>
Cc: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kairui Song <kasong@redhat.com>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Cc: Liviu Dudau <liviu.dudau@arm.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Niklas Schnelle <schnelle@linux.ibm.com>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Cc: openrisc@lists.librecores.org
Cc: Palmer Dabbelt <palmerdabbelt@google.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: "Pavel Machek (CIP)" <pavel@denx.de>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Pierre Morel <pmorel@linux.ibm.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Rich Felker <dalias@libc.org>
Cc: Robert Richter <rric@kernel.org>
Cc: Rob Herring <robh@kernel.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Cc: sparclinux@vger.kernel.org
Cc: Stafford Horne <shorne@gmail.com>
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Theodore Dubois <tblodt@icloud.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: William Cohen <wcohen@redhat.com>
Cc: Xiaoming Ni <nixiaoming@huawei.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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