x86/kasan: Print original address on #GP

Make #GP exceptions caused by out-of-bounds KASAN shadow accesses easier
to understand by computing the address of the original access and
printing that. More details are in the comments in the patch.

This turns an error like this:

  kasan: CONFIG_KASAN_INLINE enabled
  kasan: GPF could be caused by NULL-ptr deref or user memory access
  general protection fault, probably for non-canonical address
      0xe017577ddf75b7dd: 0000 [#1] PREEMPT SMP KASAN PTI

into this:

  general protection fault, probably for non-canonical address
      0xe017577ddf75b7dd: 0000 [#1] PREEMPT SMP KASAN PTI
  KASAN: maybe wild-memory-access in range
      [0x00badbeefbadbee8-0x00badbeefbadbeef]

The hook is placed in architecture-independent code, but is currently
only wired up to the X86 exception handler because I'm not sufficiently
familiar with the address space layout and exception handling mechanisms
on other architectures.

Signed-off-by: Jann Horn <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Reviewed-by: Dmitry Vyukov <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Andrey Konovalov <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Cc: linux-mm <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: x86-ml <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 8995bf10c97c..ae64ec7f752f 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -427,6 +427,8 @@ void die_addr(const char *str, struct pt_regs *regs, long err, long gp_addr)
 	int sig = SIGSEGV;
 
 	__die_header(str, regs, err);
+	if (gp_addr)
+		kasan_non_canonical_hook(gp_addr);
 	if (__die_body(str, regs, err))
 		sig = 0;
 	oops_end(flags, regs, sig);