4.20-stable review patch. If anyone has any objections, please let me know.
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[ 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... 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: