From: Borislav Petkov <bp@xxxxxxx>
commit 1acd85feba81084fcef00b73fc1601e42b77c5d8 upstream.
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 <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
Link: https://lore.kernel.org/r/20211217102029.GA29708@kili
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/cpu/mce/severity.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- 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_
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
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;
