Messages in this thread Patch in this message |  | | Date | Thu, 13 Feb 2014 08:18:24 -0800 | From | "tip-bot for H. Peter Anvin" <> | Subject | [tip:x86/urgent] x86, smap: smap_violation() is bogus if CONFIG_X86_SMAP is off |
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Commit-ID: af0c23df96fbc16089e8eda4b94b7d69b845f81e Gitweb: http://git.kernel.org/tip/af0c23df96fbc16089e8eda4b94b7d69b845f81e Author: H. Peter Anvin <hpa@linux.intel.com> AuthorDate: Thu, 13 Feb 2014 07:46:04 -0800 Committer: H. Peter Anvin <hpa@linux.intel.com> CommitDate: Thu, 13 Feb 2014 08:08:58 -0800
x86, smap: smap_violation() is bogus if CONFIG_X86_SMAP is off
If CONFIG_X86_SMAP is disabled, smap_violation() tests for conditions which are incorrect (as the AC flag doesn't matter), causing spurious faults.
The dynamic disabling of SMAP (nosmap on the command line) is fine because it disables X86_FEATURE_SMAP, therefore causing the static_cpu_has() to return false.
Found by Fengguang Wu's test system.
[ v2: use IS_ENABLED() instead of #ifdef ]
Reported-by: Fengguang Wu <fengguang.wu@intel.com> Link: http://lkml.kernel.org/r/20140213124550.GA30497@localhost Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Cc: <stable@vger.kernel.org> # v3.7+ --- arch/x86/mm/fault.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 9d591c8..824b445 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1087,7 +1087,7 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code) if (unlikely(error_code & PF_RSVD)) pgtable_bad(regs, error_code, address); - if (static_cpu_has(X86_FEATURE_SMAP)) { + if (IS_ENABLED(CONFIG_X86_SMAP) && static_cpu_has(X86_FEATURE_SMAP)) { if (unlikely(smap_violation(error_code, regs))) { bad_area_nosemaphore(regs, error_code, address); return;
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