Commit 4640c7ee authored by H. Peter Anvin's avatar H. Peter Anvin
Browse files

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.

[ v3: move all predicates into smap_violation() ]
[ v2: use IS_ENABLED() instead of #ifdef ]
Reported-by: default avatarFengguang Wu <fengguang.wu@intel.com>
Link: http://lkml.kernel.org/r/20140213124550.GA30497@localhost

Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
Cc: <stable@vger.kernel.org> # v3.7+
parent 03bbd596
......@@ -1001,6 +1001,12 @@ static int fault_in_kernel_space(unsigned long address)
static inline bool smap_violation(int error_code, struct pt_regs *regs)
{
if (!IS_ENABLED(CONFIG_X86_SMAP))
return false;
if (!static_cpu_has(X86_FEATURE_SMAP))
return false;
if (error_code & PF_USER)
return false;
......@@ -1087,11 +1093,9 @@ __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;
}
/*
......
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment