[PATCH] lib/crypto: poly1305: Use memzero_explicit() in poly1305_final()

[Eric Biggers <ebiggers@kernel.org>]

Use memzero_explicit() instead of a plain struct assignment to guarantee
zeroization of the 'struct poly1305_desc_ctx'.

Note that dead store elimination was only theoretically possible with
link-time optimization here.  But it's still worth fixing.

Fixes: a1d93064094c ("crypto: poly1305 - expose init/update/final library interface")
Cc: stable@vger.kernel.org
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/bug/linux-c3a6bd76-f6ab-4203-892a-cd06f7aa0c34
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
---
 lib/crypto/poly1305.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/crypto/poly1305.c b/lib/crypto/poly1305.c
index f313ccc4b4dd2..048c7afe86138 100644
--- a/lib/crypto/poly1305.c
+++ b/lib/crypto/poly1305.c
@@ -78,7 +78,7 @@ void poly1305_final(struct poly1305_desc_ctx *desc, u8 *dst)
 	}
 
 	poly1305_emit(&desc->state.h, dst, desc->s);
-	*desc = (struct poly1305_desc_ctx){};
+	memzero_explicit(desc, sizeof(*desc));
 }
 EXPORT_SYMBOL(poly1305_final);
 

base-commit: 6a50ce0af5c91fd665d65d357af8ae55db1df7d0
-- 
2.56.0