From ebb53e2597e2dc7637ab213df006e99681b6ee25 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Wed, 21 Nov 2018 15:11:23 -0800 Subject: [PATCH] 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 Cc: Borislav Petkov Cc: Dave Hansen Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Cc: Yu-cheng Yu Link: http://lkml.kernel.org/r/9999f151d72ff352265f3274c5ab3a4105090f49.1542841400.git.luto@kernel.org Signed-off-by: Ingo Molnar --- 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 82881bc..ca38bd0 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -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: -- 2.7.4