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lib/crypto: poly1305: Restore dependency of arch code on !KMSAN

PATCH In review Eric Biggers 2 participants 2 messages Oct 22, 2025

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Eric Biggers

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PATCH 1/1 lib/crypto: poly1305: Restore dependency of arch code on !KMSAN

Restore the dependency of the architecture-optimized Poly1305 code on !KMSAN. It was dropped by commit b646b782e522 ("lib/crypto: poly1305:
Consolidate into single module").

Unlike the other hash algorithms in lib/crypto/ (e.g., SHA-512), the way the architecture-optimized Poly1305 code is integrated results in assembly code initializing memory, for several different architectures. Thus, it generates false positive KMSAN warnings. These could be suppressed with kmsan_unpoison_memory(), but it would be needed in quite a few places. For now let's just restore the dependency on !KMSAN.

Note: this should have been caught by running poly1305_kunit with CONFIG_KMSAN=y, which I did. However, due to an unrelated KMSAN bug
(https://lore.kernel.org/r/20251022030213.GA35717@sol/), KMSAN currently isn't working reliably. Thus, the warning wasn't noticed until later.

Fixes b646b782e522 ("lib/crypto: poly1305: Consolidate into single module")
Reported-by [email protected]
Closes https://lore.kernel.org/r/[email protected]/ open here
Reported-by Pei Xiao <[email protected]>
Closes https://lore.kernel.org/r/751b3d80293a6f599bb07770afcef24f623c7da0.1761026343.git.xiaopei01@kylinos.cn/ open here
Signed-off-by Eric Biggers <[email protected]>
---
 lib/crypto/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
lib/crypto/Kconfig +1 -1
index eea17e36a22be..8886055e938f2 100644
@@ -95,11 +95,11 @@ config CRYPTO_LIB_POLY1305
 	  The Poly1305 library functions.  Select this if your module uses any
 	  of the functions from <crypto/poly1305.h>.
 
 config CRYPTO_LIB_POLY1305_ARCH
 	bool
-	depends on CRYPTO_LIB_POLY1305 && !UML
+	depends on CRYPTO_LIB_POLY1305 && !UML && !KMSAN
 	default y if ARM
 	default y if ARM64 && KERNEL_MODE_NEON
 	default y if MIPS
 	# The PPC64 code needs to be fixed to work in softirq context.
 	default y if PPC64 && CPU_LITTLE_ENDIAN && VSX && BROKEN

base-commit: 552c50713f273b494ac6c77052032a49bc9255e2

Signature · 1 line
2.51.1.dirty
maintainer Reviewed-by on v1 1/1
#1 lore raw
Quoted 23 lines · Eric Biggers

Restore the dependency of the architecture-optimized Poly1305 code on !KMSAN. It was dropped by commit b646b782e522 ("lib/crypto: poly1305:
Consolidate into single module").

Unlike the other hash algorithms in lib/crypto/ (e.g., SHA-512), the way the architecture-optimized Poly1305 code is integrated results in assembly code initializing memory, for several different architectures. Thus, it generates false positive KMSAN warnings. These could be suppressed with kmsan_unpoison_memory(), but it would be needed in quite a few places. For now let's just restore the dependency on !KMSAN.

Note: this should have been caught by running poly1305_kunit with CONFIG_KMSAN=y, which I did. However, due to an unrelated KMSAN bug
(https://lore.kernel.org/r/20251022030213.GA35717@sol/), KMSAN currently isn't working reliably. Thus, the warning wasn't noticed until later.

Fixes b646b782e522 ("lib/crypto: poly1305: Consolidate into single module")
Reported-by [email protected]
Closes https://lore.kernel.org/r/[email protected]/ open here
Reported-by Pei Xiao <[email protected]>
Closes https://lore.kernel.org/r/751b3d80293a6f599bb07770afcef24f623c7da0.1761026343.git.xiaopei01@kylinos.cn/ open here
Signed-off-by Eric Biggers <[email protected]>
Quoted 4 lines
---
 lib/crypto/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
Reviewed-by Ard Biesheuvel <[email protected]>