| From | Sasha Levin <> | Subject | [PATCH AUTOSEL 4.20 024/117] x86/fault: Don't try to recover from an implicit supervisor access | Date | Tue, 8 Jan 2019 14:24:52 -0500 |
| |
From: Andy Lutomirski <luto@kernel.org>
[ Upstream commit ebb53e2597e2dc7637ab213df006e99681b6ee25 ]
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> Signed-off-by: Sasha Levin <sashal@kernel.org> --- arch/x86/mm/fault.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 71d4b9d4d43f..26388576a599 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -639,6 +639,15 @@ 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)) { /* @@ -726,6 +735,7 @@ 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: -- 2.19.1
|