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| author | Ard Biesheuvel <ardb@kernel.org> | 2021-10-15 17:27:09 +0300 |
|---|---|---|
| committer | Ard Biesheuvel <ardb@kernel.org> | 2021-12-03 17:11:31 +0300 |
| commit | eae9523fdd7a6c592e80666681962acbd913cda2 (patch) | |
| tree | 16e293d6b1d12f0e5253407adc48d36c93547068 | |
| parent | 4ab6827081c63b83011a18d8e27f621ed34b1194 (diff) | |
| download | linux-eae9523fdd7a6c592e80666681962acbd913cda2.tar.xz | |
ARM: backtrace-clang: avoid crash on bogus frame pointer
The Clang backtrace code dereferences the link register value pulled
from the stack to decide whether the caller was a branch-and-link
instruction, in order to subsequently decode the offset to find the
start of the calling function. Unlike other loads in this routine, this
one is not protected by a fixup, and may therefore cause a crash if the
address in question is bogus.
So let's fix this, by treating the fault as a failure to decode the 'bl'
instruction. To avoid a label renum, reuse a fixup label that guards an
instruction that cannot fault to begin with.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M
| -rw-r--r-- | arch/arm/lib/backtrace-clang.S | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/arch/arm/lib/backtrace-clang.S b/arch/arm/lib/backtrace-clang.S index 5b2cdb1003e3..5b4bca85d06d 100644 --- a/arch/arm/lib/backtrace-clang.S +++ b/arch/arm/lib/backtrace-clang.S @@ -144,7 +144,7 @@ for_each_frame: tst frame, mask @ Check for address exceptions */ 1003: ldr sv_lr, [sv_fp, #4] @ get saved lr from next frame - ldr r0, [sv_lr, #-4] @ get call instruction +1004: ldr r0, [sv_lr, #-4] @ get call instruction ldr r3, .Lopcode+4 and r2, r3, r0 @ is this a bl call teq r2, r3 @@ -164,7 +164,7 @@ finished_setup: /* * Print the function (sv_pc) and where it was called from (sv_lr). */ -1004: mov r0, sv_pc + mov r0, sv_pc mov r1, sv_lr mov r2, frame @@ -210,7 +210,7 @@ ENDPROC(c_backtrace) .long 1001b, 1006b .long 1002b, 1006b .long 1003b, 1006b - .long 1004b, 1006b + .long 1004b, finished_setup .long 1005b, 1006b .popsection |