Commit-ID: ebb53e2597e2dc7637ab213df006e99681b6ee25
Gitweb: https://git.kernel.org/tip/ebb53e2597e2dc7637ab213df006e99681b6ee25
Author: Andy Lutomirski <luto@xxxxxxxxxx>
AuthorDate: Wed, 21 Nov 2018 15:11:23 -0800
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Thu, 22 Nov 2018 09:23:00 +0100
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@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
Link: http://lkml.kernel.org/r/9999f151d72ff352265f3274c5ab3a4105090f49.1542841400.git.luto@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
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 82881bc5feef..ca38bd0472f2 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:
|