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authorAndy Lutomirski <luto@amacapital.net>2014-10-25 02:58:12 +0400
committerIngo Molnar <mingo@kernel.org>2015-02-04 14:10:47 +0300
commit7911d3f7af14a614617e38245fedf98a724e46a9 (patch)
tree8a8d163aee11daadeda7ecd9e835b86c2eb5890e /arch/x86/include/asm/mmu.h
parentc1317ec2b906442930318d9d6e51425c5a69e9cb (diff)
downloadlinux-7911d3f7af14a614617e38245fedf98a724e46a9.tar.xz
perf/x86: Only allow rdpmc if a perf_event is mapped
We currently allow any process to use rdpmc. This significantly weakens the protection offered by PR_TSC_DISABLED, and it could be helpful to users attempting to exploit timing attacks. Since we can't enable access to individual counters, use a very coarse heuristic to limit access to rdpmc: allow access only when a perf_event is mmapped. This protects seccomp sandboxes. There is plenty of room to further tighen these restrictions. For example, this allows rdpmc for any x86_pmu event, but it's only useful for self-monitoring tasks. As a side effect, cap_user_rdpmc will now be false for AMD uncore events. This isn't a real regression, since .event_idx is disabled for these events anyway for the time being. Whenever that gets re-added, the cap_user_rdpmc code can be adjusted or refactored accordingly. Signed-off-by: Andy Lutomirski <luto@amacapital.net> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Kees Cook <keescook@chromium.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Vince Weaver <vince@deater.net> Cc: "hillf.zj" <hillf.zj@alibaba-inc.com> Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/a2bdb3cf3a1d70c26980d7c6dddfbaa69f3182bf.1414190806.git.luto@amacapital.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/include/asm/mmu.h')
-rw-r--r--arch/x86/include/asm/mmu.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h
index 876e74e8eec7..09b9620a73b4 100644
--- a/arch/x86/include/asm/mmu.h
+++ b/arch/x86/include/asm/mmu.h
@@ -19,6 +19,8 @@ typedef struct {
struct mutex lock;
void __user *vdso;
+
+ atomic_t perf_rdpmc_allowed; /* nonzero if rdpmc is allowed */
} mm_context_t;
#ifdef CONFIG_SMP