From 1acd85feba81084fcef00b73fc1601e42b77c5d8 Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Fri, 17 Dec 2021 16:49:25 +0100 Subject: [PATCH] x86/mce: Check regs before accessing it Commit in Fixes accesses pt_regs before checking whether it is NULL or not. Make sure the NULL pointer check happens first. Fixes: 0a5b288e85bb ("x86/mce: Prevent severity computation from being instrumented") Reported-by: Dan Carpenter Signed-off-by: Borislav Petkov Reviewed-by: Tony Luck Link: https://lore.kernel.org/r/20211217102029.GA29708@kili --- arch/x86/kernel/cpu/mce/severity.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/cpu/mce/severity.c b/arch/x86/kernel/cpu/mce/severity.c index a326467697051..7aa2bda93cbb6 100644 --- a/arch/x86/kernel/cpu/mce/severity.c +++ b/arch/x86/kernel/cpu/mce/severity.c @@ -222,6 +222,9 @@ static bool is_copy_from_user(struct pt_regs *regs) struct insn insn; int ret; + if (!regs) + return false; + if (copy_from_kernel_nofault(insn_buf, (void *)regs->ip, MAX_INSN_SIZE)) return false; @@ -283,7 +286,7 @@ static noinstr int error_context(struct mce *m, struct pt_regs *regs) switch (fixup_type) { case EX_TYPE_UACCESS: case EX_TYPE_COPY: - if (!regs || !copy_user) + if (!copy_user) return IN_KERNEL; m->kflags |= MCE_IN_KERNEL_COPYIN; fallthrough; -- 2.30.2