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2023-11-08x86/shstk: Delay signal entry SSP write until after user accessesRick Edgecombe1-3/+3
When a signal is being delivered, the kernel needs to make accesses to userspace. These accesses could encounter an access error, in which case the signal delivery itself will trigger a segfault. Usually this would result in the kernel killing the process. But in the case of a SEGV signal handler being configured, the failure of the first signal delivery will result in *another* signal getting delivered. The second signal may succeed if another thread has resolved the issue that triggered the segfault (i.e. a well timed mprotect()/mmap()), or the second signal is being delivered to another stack (i.e. an alt stack). On x86, in the non-shadow stack case, all the accesses to userspace are done before changes to the registers (in pt_regs). The operation is aborted when an access error occurs, so although there may be writes done for the first signal, control flow changes for the signal (regs->ip, regs->sp, etc) are not committed until all the accesses have already completed successfully. This means that the second signal will be delivered as if it happened at the time of the first signal. It will effectively replace the first aborted signal, overwriting the half-written frame of the aborted signal. So on sigreturn from the second signal, control flow will resume happily from the point of control flow where the original signal was delivered. The problem is, when shadow stack is active, the shadow stack SSP register/MSR is updated *before* some of the userspace accesses. This means if the earlier accesses succeed and the later ones fail, the second signal will not be delivered at the same spot on the shadow stack as the first one. So on sigreturn from the second signal, the SSP will be pointing to the wrong location on the shadow stack (off by a frame). Pengfei privately reported that while using a shadow stack enabled glibc, the “signal06” test in the LTP test-suite hung. It turns out it is testing the above described double signal scenario. When this test was compiled with shadow stack, the first signal pushed a shadow stack sigframe, then the second pushed another. When the second signal was handled, the SSP was at the first shadow stack signal frame instead of the original location. The test then got stuck as the #CP from the twice incremented SSP was incorrect and generated segfaults in a loop. Fix this by adjusting the SSP register only after any userspace accesses, such that there can be no failures after the SSP is adjusted. Do this by moving the shadow stack sigframe push logic to happen after all other userspace accesses. Note, sigreturn (as opposed to the signal delivery dealt with in this patch) has ordering behavior that could lead to similar failures. The ordering issues there extend beyond shadow stack to include the alt stack restoration. Fixing that would require cross-arch changes, and the ordering today does not cause any known test or apps breakages. So leave it as is, for now. [ dhansen: minor changelog/subject tweak ] Fixes: 05e36022c054 ("x86/shstk: Handle signals for shadow stack") Reported-by: Pengfei Xu <pengfei.xu@intel.com> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Tested-by: Pengfei Xu <pengfei.xu@intel.com> Cc:stable@vger.kernel.org Link: https://lore.kernel.org/all/20231107182251.91276-1-rick.p.edgecombe%40intel.com Link: https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/syscalls/signal/signal06.c
2023-08-03x86/shstk: Handle signals for shadow stackRick Edgecombe1-0/+6
When a signal is handled, the context is pushed to the stack before handling it. For shadow stacks, since the shadow stack only tracks return addresses, there isn't any state that needs to be pushed. However, there are still a few things that need to be done. These things are visible to userspace and which will be kernel ABI for shadow stacks. One is to make sure the restorer address is written to shadow stack, since the signal handler (if not changing ucontext) returns to the restorer, and the restorer calls sigreturn. So add the restorer on the shadow stack before handling the signal, so there is not a conflict when the signal handler returns to the restorer. The other thing to do is to place some type of checkable token on the thread's shadow stack before handling the signal and check it during sigreturn. This is an extra layer of protection to hamper attackers calling sigreturn manually as in SROP-like attacks. For this token the shadow stack data format defined earlier can be used. Have the data pushed be the previous SSP. In the future the sigreturn might want to return back to a different stack. Storing the SSP (instead of a restore offset or something) allows for future functionality that may want to restore to a different stack. So, when handling a signal push - the SSP pointing in the shadow stack data format - the restorer address below the restore token. In sigreturn, verify SSP is stored in the data format and pop the shadow stack. Co-developed-by: Yu-cheng Yu <yu-cheng.yu@intel.com> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Mike Rapoport (IBM) <rppt@kernel.org> Tested-by: Pengfei Xu <pengfei.xu@intel.com> Tested-by: John Allen <john.allen@amd.com> Tested-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/all/20230613001108.3040476-32-rick.p.edgecombe%40intel.com
2023-08-03x86/shstk: Add user control-protection fault handlerRick Edgecombe1-1/+1
A control-protection fault is triggered when a control-flow transfer attempt violates Shadow Stack or Indirect Branch Tracking constraints. For example, the return address for a RET instruction differs from the copy on the shadow stack. There already exists a control-protection fault handler for handling kernel IBT faults. Refactor this fault handler into separate user and kernel handlers, like the page fault handler. Add a control-protection handler for usermode. To avoid ifdeffery, put them both in a new file cet.c, which is compiled in the case of either of the two CET features supported in the kernel: kernel IBT or user mode shadow stack. Move some static inline functions from traps.c into a header so they can be used in cet.c. Opportunistically fix a comment in the kernel IBT part of the fault handler that is on the end of the line instead of preceding it. Keep the same behavior for the kernel side of the fault handler, except for converting a BUG to a WARN in the case of a #CP happening when the feature is missing. This unifies the behavior with the new shadow stack code, and also prevents the kernel from crashing under this situation which is potentially recoverable. The control-protection fault handler works in a similar way as the general protection fault handler. It provides the si_code SEGV_CPERR to the signal handler. Co-developed-by: Yu-cheng Yu <yu-cheng.yu@intel.com> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Mike Rapoport (IBM) <rppt@kernel.org> Tested-by: Pengfei Xu <pengfei.xu@intel.com> Tested-by: John Allen <john.allen@amd.com> Tested-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/all/20230613001108.3040476-28-rick.p.edgecombe%40intel.com
2023-01-06x86/signal/compat: Move sigaction_compat_abi() to signal_64.cBrian Gerst1-0/+13
Also remove the now-empty signal_compat.c. Signed-off-by: Brian Gerst <brgerst@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20221219193904.190220-3-brgerst@gmail.com Cc: Al Viro <viro@zeniv.linux.org.uk>
2023-01-06x86/signal: Move siginfo field testsBrian Gerst1-0/+114
Move the tests to the appropriate signal_$(BITS).c file. Convert them to use static_assert(), removing the need for a dummy function. Signed-off-by: Brian Gerst <brgerst@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20221219193904.190220-2-brgerst@gmail.com Cc: Al Viro <viro@zeniv.linux.org.uk>
2022-10-19x86/signal/64: Move 64-bit signal code to its own fileBrian Gerst1-0/+383
[ bp: Fixup merge conflict caused by changes coming from the kbuild tree. ] Signed-off-by: Brian Gerst <brgerst@gmail.com> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: "Eric W. Biederman" <ebiederm@xmission.com> Link: https://lore.kernel.org/r/20220606203802.158958-9-brgerst@gmail.com Signed-off-by: Borislav Petkov <bp@suse.de>
2008-11-26x86: signal: unify signal_{32|64}.cHiroshi Shimamoto1-915/+0
Impact: cleanup Unify signal_{32|64}.c! Mechanic unification - the two files are the same. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-26x86: signal: unify signal_{32|64}.c, prepareHiroshi Shimamoto1-1/+115
Impact: cleanup Add #ifdef directive for 32-bit only code. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-26x86: signal: cosmetic unification of __setup_sigframe() and ↵Hiroshi Shimamoto1-53/+256
__setup_rt_sigframe() Impact: cleanup Add #ifdef directive to unify __setup_sigframe() and __setup_rt_sigframe(). Move them after {setup|restore}_sigcontext() declaration. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-26x86: signal: move {setup|restore}_sigcontext()Hiroshi Shimamoto1-74/+74
Impact: cleanup Move {setup|restore}_sigcontext() declaration onto head of file. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-23x86: signal: cosmetic unification of sys_rt_sigreturn()Hiroshi Shimamoto1-0/+9
Impact: cleanup Add #ifdef directive for unification. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-23x86: signal: cosmetic unification of sys_sigaltstack()Hiroshi Shimamoto1-0/+15
Impact: cleanup Add #ifdef directive for unification. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-23x86: signal: cosmetic unification of including headersHiroshi Shimamoto1-1/+6
Impact: cleanup Make the headers portion of signal_32.c and signal_64.c the same. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-21x86: signal: rename COPY_SEG_STRICT to COPY_SEG_CPL3Hiroshi Shimamoto1-4/+4
Impact: cleanup Rename macro COPY_SEG_STRICT to COPY_SEG_CPL3, as suggested by hpa. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-08x86: signal: cosmetic unification of setup_sigcontext()Hiroshi Shimamoto1-5/+28
Impact: cleanup Make setup_sigcontext() same. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-06x86: signal_64: make setup_sigcontext() similarHiroshi Shimamoto1-7/+5
Impact: cleanup remove passing task struct. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-06x86: signal_64: setup fpstate in setup_sigcontext()Hiroshi Shimamoto1-4/+6
Impact: cleanup set fpstate field of signal context at setup_sigcontext(). Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-04x86: signal_64: remove unused code in __setup_rt_frame()Hiroshi Shimamoto1-5/+1
Impact: cleanup sizeof(*set) is always 8 on x86_64. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-30x86: signal: cosmetic unification of NR_restart_syscallHiroshi Shimamoto1-0/+5
Impact: cleanup Add #ifdef directive to unify NR_restart_syscall. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-30x86: signal: cosmetic unification of macros for setup_rt_frame()Hiroshi Shimamoto1-2/+12
Impact: cleanup Add #ifdef directive for unification. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-30x86: signal: cosmetic unification of signr_convert()Hiroshi Shimamoto1-0/+6
Impact: cleanup Make signr_convert() same. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-27x86: signal_64.c: get_stack() doesn't need entire regsHiroshi Shimamoto1-6/+4
Impact: cleanup get_stack() uses sp only, entire regs is not needed. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-27x86: signal: cosmetic unification of restore_sigcontext()Hiroshi Shimamoto1-0/+15
Impact: cleanup Make restore_sigcontext() the same. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-03x86: signal: remove indent in restore_sigcontext()Hiroshi Shimamoto1-12/+7
remove braces and indent for flags and fpstate in restore_sigcontext(). Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-03x86: signal: move macros out from restore_sigcontext()Hiroshi Shimamoto1-7/+11
move macros, COPY, COPY_SEG*, GET_SEG, out from restore_sigcontext(). x86_64: introduce COPY_SEG_STRICT for cs. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-25x86: signal: introduce helper macro is_ia32Hiroshi Shimamoto1-4/+9
Introduce new macro is_ia32 for unification of setup_rt_frame(). No effect in binary, compiler will optimize. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-25x86: signal_64.c: introduce helper function signr_convert()Hiroshi Shimamoto1-2/+8
This helper function is for unification of setup_rt_frame(). No effect in binary. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-24x86: signal: cosmetic unification of handle_signal()Hiroshi Shimamoto1-0/+2
Make handle_signal() same. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-24x86: signal: cosmetic unification of do_notify_resume()Hiroshi Shimamoto1-4/+12
Make do_notify_resume() same. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-24x86: signal: cosmetic unification of do_signal()Hiroshi Shimamoto1-2/+4
Make do_signal() same. Thia patch modifies only comments in signal_64.c. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-14x86: signal: introduce do_rt_sigreturn()Hiroshi Shimamoto1-3/+8
introduce do_rt_sigreturn(), to collect common part of sys_rt_sigreturn(). No change in functionality intended. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-14x86: signal: remove unneeded err handlingHiroshi Shimamoto1-3/+2
This patch eliminates unused or unneeded variable handling. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-14x86: signal: put give_sigsegv of setup frames togetherHiroshi Shimamoto1-8/+9
When setup frame fails, force_sigsegv is called and returns -EFAULT. There is similar code in ia32_setup_frame(), ia32_setup_rt_frame(), __setup_frame() and __setup_rt_frame(). Make them identical. No change in functionality intended. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-10x86: signal_64.c: make handle_signal() similarHiroshi Shimamoto1-28/+29
Make handle_signal() same as 32bit. No change in functionality intended. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-10x86: signal_64.c: arg for restore_i387_xstate() is void __user *Hiroshi Shimamoto1-1/+2
restore_i387_xstate() is declared as: int restore_i387_xstate(void __user *buf); so, make the variable buf void __user *. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-10x86: signal_64.c: clean up signal_fault()Hiroshi Shimamoto1-4/+6
clean up and make signal_fault() same as 32bit. Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-06x86: signal: split out frame setupsHiroshi Shimamoto1-10/+20
Make setup_rt_frame() and split out frame setups from handle_signal(). This is for cosmetic unification of handle_signal(). Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-06x86: signal: make NR_restart_syscallHiroshi Shimamoto1-3/+3
make NR_restart_syscall macro for cosmetic unification of handle_signal(). Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-06Merge branch 'x86/cleanups' into x86/signalIngo Molnar1-29/+27
Conflicts: arch/x86/kernel/signal_64.c Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-06Merge branches 'x86/tracehook', 'x86/xsave' and 'x86/prototypes' into x86/signalIngo Molnar1-121/+24
Conflicts: arch/x86/kernel/signal_64.c Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-05Merge branch 'linus' into x86/tracehookIngo Molnar1-1/+10
2008-08-20Merge branch 'linus' into x86/cleanupsIngo Molnar1-1/+10
2008-08-14Merge commit 'v2.6.27-rc3' into x86/prototypesIngo Molnar1-3/+53
Conflicts: include/asm-x86/dma-mapping.h Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-08-14x86, xsave: remove the redundant access_ok() in setup_rt_frame()Suresh Siddha1-3/+0
save_i387_xstate() is already doing the required access_ok(). Remove the redundant access_ok() before it. Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-31x86: coding style fixes to arch/x86/kernel/signal_64.cGustavo F. Padovan1-32/+30
Fix all errors and many warnings reported by checkpatch.pl without change signal_64.o arch/x86/kernel/signal_64.o text data bss dec hex filename 5143 0 8 5151 141f signal_64.o.after 5143 0 8 5151 141f signal_64.o.before md5: e68718092b3641cb27e79e55ce57e3ad signal_64.o.after e68718092b3641cb27e79e55ce57e3ad signal_64.o.before Signed-off-by: Gustavo F. Padovan <gustavo@las.ic.unicamp.br> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-30x86, xsave: save/restore the extended state context in sigframeSuresh Siddha1-2/+5
On cpu's supporting xsave/xrstor, fpstate pointer in the sigcontext, will include the extended state information along with fpstate information. Presence of extended state information is indicated by the presence of FP_XSTATE_MAGIC1 at fpstate.sw_reserved.magic1 and FP_XSTATE_MAGIC2 at fpstate + (fpstate.sw_reserved.extended_size - FP_XSTATE_MAGIC2_SIZE). Extended feature bit mask that is saved in the memory layout is represented by the fpstate.sw_reserved.xstate_bv For RT signal frames, UC_FP_XSTATE in the uc_flags also indicate the presence of extended state information in the sigcontext's fpstate pointer. Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Signed-off-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-30x86, xsave: reorganization of signal save/restore fpstate code layoutSuresh Siddha1-80/+3
move 64bit routines that saves/restores fpstate in/from user stack from signal_64.c to xsave.c restore_i387_xstate() now handles the condition when user passes NULL fpstate. Other misc changes for prepartion of xsave/xrstor sigcontext support. Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Signed-off-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-30x86, xsave: dynamically allocate sigframes fpstate instead of static allocationSuresh Siddha1-1/+1
dynamically allocate fpstate on the stack, instead of static allocation in the current sigframe layout on the user stack. This will allow the fpstate structure to grow in the future, which includes extended state information supporting xsave/xrstor. signal handlers will be able to access the fpstate pointer from the sigcontext structure asusual, with no change. For the non RT sigframe's (which are supported only for 32bit apps), current static fpstate layout in the sigframe will be unused(so that we don't change the extramask[] offset in the sigframe and thus prevent breaking app's which modify extramask[]). Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Signed-off-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-27x86: tracehook: TIF_NOTIFY_RESUMERoland McGrath1-0/+5
This adds TIF_NOTIFY_RESUME support for x86, both 64-bit and 32-bit. When set, we call tracehook_notify_resume() on the way to user mode. Signed-off-by: Roland McGrath <roland@redhat.com>
2008-07-27x86 signals: use asm/syscall.hRoland McGrath1-33/+5
Replace local inlines with the asm/syscall.h interfaces that do the same things. Signed-off-by: Roland McGrath <roland@redhat.com>
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