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From: Ard Biesheuvel <ardb@kernel.org>
To: linux@armlinux.org.uk, linux-arm-kernel@lists.infradead.org
Cc: linux-hardening@vger.kernel.org, Ard Biesheuvel <ardb@kernel.org>,
	Nicolas Pitre <nico@fluxnic.net>, 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>,
	Tony Lindgren <tony@atomide.com>, Marc Zyngier <maz@kernel.org>,
	Vladimir Murzin <vladimir.murzin@arm.com>,
	Jesse Taube <mr.bossman075@gmail.com>
Subject: [PATCH v5 21/32] ARM: backtrace-clang: avoid crash on bogus frame pointer
Date: Mon, 24 Jan 2022 18:47:33 +0100	[thread overview]
Message-ID: <20220124174744.1054712-22-ardb@kernel.org> (raw)
In-Reply-To: <20220124174744.1054712-1-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>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M
---
 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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  parent reply	other threads:[~2022-01-24 18:04 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-24 17:47 [PATCH v5 00/32] ARM vmap'ed and IRQ stacks roundup Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 01/32] ARM: riscpc: drop support for IOMD_IRQREQC/IOMD_IRQREQD IRQ groups Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 02/32] ARM: riscpc: use GENERIC_IRQ_MULTI_HANDLER Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 03/32] ARM: footbridge: " Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 04/32] ARM: iop32x: offset IRQ numbers by 1 Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 05/32] ARM: iop32x: use GENERIC_IRQ_MULTI_HANDLER Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 06/32] ARM: remove old-style irq entry Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 07/32] irqchip: nvic: Use GENERIC_IRQ_MULTI_HANDLER Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 08/32] ARM: decompressor: disable stack protector Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 09/32] ARM: stackprotector: prefer compiler for TLS based per-task protector Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 10/32] ARM: entry: preserve thread_info pointer in switch_to Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 11/32] ARM: module: implement support for PC-relative group relocations Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 12/32] ARM: assembler: add optimized ldr/str macros to load variables from memory Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 13/32] ARM: percpu: add SMP_ON_UP support Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 14/32] ARM: use TLS register for 'current' on !SMP as well Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 15/32] ARM: smp: defer TPIDRURO update for SMP v6 configurations too Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 16/32] ARM: implement THREAD_INFO_IN_TASK for uniprocessor systems Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 17/32] ARM: assembler: introduce bl_r macro Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 18/32] ARM: unwind: support unwinding across multiple stacks Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 19/32] ARM: export dump_mem() to other objects Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 20/32] ARM: unwind: dump exception stack from calling frame Ard Biesheuvel
2022-01-24 17:47 ` Ard Biesheuvel [this message]
2022-01-24 17:47 ` [PATCH v5 22/32] ARM: implement IRQ stacks Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 23/32] ARM: call_with_stack: add unwind support Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 24/32] ARM: run softirqs on the per-CPU IRQ stack Ard Biesheuvel
2022-03-22  9:04   ` Sebastian Andrzej Siewior
2022-03-22  9:35     ` Ard Biesheuvel
2022-03-22 11:29       ` Sebastian Andrzej Siewior
2022-01-24 17:47 ` [PATCH v5 25/32] ARM: memcpy: use frame pointer as unwind anchor Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 26/32] ARM: memmove: " Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 27/32] ARM: memset: clean up unwind annotations Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 28/32] ARM: unwind: disregard unwind info before stack frame is set up Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 29/32] ARM: entry: rework stack realignment code in svc_entry Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 30/32] ARM: switch_to: clean up Thumb2 code path Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 31/32] ARM: mm: prepare vmalloc_seq handling for use under SMP Ard Biesheuvel
2022-01-24 17:47 ` [PATCH v5 32/32] ARM: implement support for vmap'ed stacks Ard Biesheuvel
2022-01-24 17:56 ` [PATCH v5 00/32] ARM vmap'ed and IRQ stacks roundup Russell King (Oracle)
2022-01-24 17:57   ` Ard Biesheuvel

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