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x86/mce: Check regs before accessing it

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Commit in Fixes accesses pt_regs before checking whether it is NULL or
not. Make sure the NULL pointer check happens first.

Fixes: 0a5b288e85 ("x86/mce: Prevent severity computation from being instrumented")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/r/20211217102029.GA29708@kili
This commit is contained in:
Borislav Petkov
2021-12-17 16:49:25 +01:00
parent e3d72e8eee
commit 1acd85feba
1 changed files with 4 additions and 1 deletions
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5
arch/x86/kernel/cpu/mce/severity.c
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@@ -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;