path: root/arch
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authorH. Peter Anvin <hpa@linux.intel.com>2014-02-13 07:46:04 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-02-22 12:41:27 -0800
commitd8b7ff138d2d53fee8fd5e924882c122d0e5498a (patch)
tree00225e5584b08f5992ec7574b591cc4395d4e8ce /arch
parent1416612d2bf41f0a118087847c9b6a8fcd9c87da (diff)
x86, smap: smap_violation() is bogus if CONFIG_X86_SMAP is off
commit 4640c7ee9b8953237d05a61ea3ea93981d1bc961 upstream. 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. [ v3: move all predicates into smap_violation() ] [ 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
1 files changed, 9 insertions, 5 deletions
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 654be4ae304..c1e9e4cbbd7 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -989,6 +989,12 @@ static int fault_in_kernel_space(unsigned long address)
static inline bool smap_violation(int error_code, struct pt_regs *regs)
+ return false;
+ if (!static_cpu_has(X86_FEATURE_SMAP))
+ return false;
if (error_code & PF_USER)
return false;
@@ -1091,11 +1097,9 @@ __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 (unlikely(smap_violation(error_code, regs))) {
- bad_area_nosemaphore(regs, error_code, address);
- return;
- }
+ if (unlikely(smap_violation(error_code, regs))) {
+ bad_area_nosemaphore(regs, error_code, address);
+ return;
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);