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From: Ard Biesheuvel <ardb@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: Ard Biesheuvel <ardb@kernel.org>, Marc Zyngier <maz@kernel.org>,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Kees Cook <keescook@chromium.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Mark Brown <broonie@kernel.org>
Subject: [PATCH v3 1/4] arm64: assembler: Force error on misuse of .Lframe_local_offset
Date: Fri,  9 Dec 2022 16:20:45 +0100	[thread overview]
Message-ID: <20221209152048.3517080-2-ardb@kernel.org> (raw)
In-Reply-To: <20221209152048.3517080-1-ardb@kernel.org>

The frame_push macro sets a local symbol .Lframe_local_offset to the
offset where the local variable area resides in the stack frame.
However, while we take care not to nest frame_push and frame_pop
sequences, .Lframe_local_offset retains its most recent value, allowing
it to be referenced erroneously from outside a frame_push/frame_pop
pair. So set it to an obviously wrong value that is guaranteed to
trigger a link error in frame_pop.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/include/asm/assembler.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index e5957a53be3983ac..1c04701e4fda8458 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -758,6 +758,7 @@ alternative_endif
 	.endif
 	ldp		x29, x30, [sp], #.Lframe_local_offset + .Lframe_extra
 	.set		.Lframe_regcount, -1
+	.set		.Lframe_local_offset, frame_local_offset_error
 	.endif
 	.endm
 
-- 
2.35.1


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  reply	other threads:[~2022-12-09 15:22 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-09 15:20 [PATCH v3 0/4] arm64: Add return address protection to asm code Ard Biesheuvel
2022-12-09 15:20 ` Ard Biesheuvel [this message]
2022-12-09 15:20 ` [PATCH v3 2/4] arm64: assembler: Protect return addresses in asm routines Ard Biesheuvel
2022-12-09 15:20 ` [PATCH v3 3/4] arm64: ftrace: Preserve original link register value in ftrace_regs Ard Biesheuvel
2022-12-09 15:20 ` [PATCH v3 4/4] arm64: ftrace: Add return address protection Ard Biesheuvel

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