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x86/fault: Fold smap_violation() into do_user_addr_fault()

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smap_violation() has a single caller, and the contents are a bit
nonsensical.  I'm going to fix it, but first let's fold it into its
caller for ease of comprehension.

In this particular case, the user_mode(regs) check is incorrect --
it will cause false positives in the case of a user-initiated
kernel-privileged access.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Link: http://lkml.kernel.org/r/806c366f6ca861152398ce2c01744d59d9aceb6d.1542667307.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2018-11-19 14:45:28 -08:00 committed by Ingo Molnar
parent dae0a10593
commit a15781b536
1 changed files with 6 additions and 17 deletions
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23
arch/x86/mm/fault.c
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@ -1148,20 +1148,6 @@ static int fault_in_kernel_space(unsigned long address)
return address >= TASK_SIZE_MAX;
}
static inline bool smap_violation(int error_code, struct pt_regs *regs)
{
if (!cpu_feature_enabled(X86_FEATURE_SMAP))
return false;
if (error_code & X86_PF_USER)
return false;
if (!user_mode(regs) && (regs->flags & X86_EFLAGS_AC))
return false;
return true;
}
/*
* Called for all faults where 'address' is part of the kernel address
* space. Might get called for faults that originate from *code* that
@ -1249,10 +1235,13 @@ void do_user_addr_fault(struct pt_regs *regs,
pgtable_bad(regs, hw_error_code, address);
/*
* Check for invalid kernel (supervisor) access to user
* pages in the user address space.
* If SMAP is on, check for invalid kernel (supervisor)
* access to user pages in the user address space.
*/
if (unlikely(smap_violation(hw_error_code, regs))) {
if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) &&
!(hw_error_code & X86_PF_USER) &&
(user_mode(regs) || !(regs->flags & X86_EFLAGS_AC))))
{
bad_area_nosemaphore(regs, hw_error_code, address);
return;
}