From: Ard Biesheuvel <ardb@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: Ard Biesheuvel <ardb@kernel.org>,
Russell King <linux@armlinux.org.uk>,
Arnd Bergmann <arnd@arndb.de>, Kees Cook <keescook@chromium.org>,
Keith Packard <keithpac@amazon.com>,
Linus Walleij <linus.walleij@linaro.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Nicolas Pitre <nico@fluxnic.net>
Subject: [PATCH v3 07/10] ARM: backtrace-clang: avoid crash on bogus frame pointer
Date: Sun, 17 Oct 2021 15:17:20 +0200 [thread overview]
Message-ID: <20211017131723.4034662-8-ardb@kernel.org> (raw)
In-Reply-To: <20211017131723.4034662-1-ardb@kernel.org>
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>
---
arch/arm/lib/backtrace-clang.S | 6 +++---
1 file 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
--
2.30.2
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next prev parent reply other threads:[~2021-10-17 13:20 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-17 13:17 [PATCH v3 00/10] ARM: add support for IRQ stacks Ard Biesheuvel
2021-10-17 13:17 ` [PATCH v3 01/10] ARM: remove some dead code Ard Biesheuvel
2021-10-17 13:17 ` [PATCH v3 02/10] ARM: assembler: introduce bl_r and bl_m macros Ard Biesheuvel
2021-10-17 13:17 ` [PATCH v3 03/10] ARM: optimize indirect call to handle_arch_irq for v7 cores Ard Biesheuvel
2021-10-17 13:17 ` [PATCH v3 04/10] ARM: unwind: support unwinding across multiple stacks Ard Biesheuvel
2021-10-17 13:17 ` [PATCH v3 05/10] ARM: export dump_mem() to other objects Ard Biesheuvel
2021-10-17 13:17 ` [PATCH v3 06/10] ARM: unwind: dump exception stack from calling frame Ard Biesheuvel
2021-10-17 13:17 ` Ard Biesheuvel [this message]
2021-10-18 19:58 ` [PATCH v3 07/10] ARM: backtrace-clang: avoid crash on bogus frame pointer Nick Desaulniers
2021-10-17 13:17 ` [PATCH v3 08/10] ARM: implement IRQ stacks Ard Biesheuvel
2021-10-18 20:43 ` Nick Desaulniers
2021-10-18 20:59 ` Ard Biesheuvel
2021-10-18 21:03 ` Nick Desaulniers
2021-10-17 13:17 ` [PATCH v3 09/10] ARM: call_with_stack: add unwind support Ard Biesheuvel
2021-10-18 20:50 ` Nick Desaulniers
2021-10-17 13:17 ` [PATCH v3 10/10] ARM: run softirqs on the per-CPU IRQ stack Ard Biesheuvel
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