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x86/fault: Don't try to recover from an implicit supervisor access 

This avoids a situation in which we attempt to apply various fixups
that are not intended to handle implicit supervisor accesses from
user mode if we screw up in a way that causes this type of fault.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.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/9999f151d72ff352265f3274c5ab3a4105090f49.1542841400.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2018-11-21 15:11:23 -08:00 committed by Ingo Molnar
parent 0ed32f1aa6
commit ebb53e2597
1 changed files with 10 additions and 0 deletions
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10
arch/x86/mm/fault.c
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@ -653,6 +653,15 @@ no_context(struct pt_regs *regs, unsigned long error_code,
unsigned long flags;
int sig;
if (user_mode(regs)) {
/*
* This is an implicit supervisor-mode access from user
* mode. Bypass all the kernel-mode recovery code and just
* OOPS.
*/
goto oops;
}
/* Are we prepared to handle this kernel fault? */
if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) {
/*
@ -738,6 +747,7 @@ no_context(struct pt_regs *regs, unsigned long error_code,
if (IS_ENABLED(CONFIG_EFI))
efi_recover_from_page_fault(address);
oops:
/*
* Oops. The kernel tried to access some bad page. We'll have to
* terminate things with extreme prejudice: