#syz test
---
 lib/crypto/poly1305.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/crypto/poly1305.c b/lib/crypto/poly1305.c
index f313ccc4b4dd..25018e3fb487 100644
--- a/lib/crypto/poly1305.c
+++ b/lib/crypto/poly1305.c
@@ -13,6 +13,7 @@
 #include <linux/module.h>
 #include <linux/string.h>
 #include <linux/unaligned.h>
+#include <linux/kmsan.h>
 
 #ifdef CONFIG_CRYPTO_LIB_POLY1305_ARCH
 #include "poly1305.h" /* $(SRCARCH)/poly1305.h */
@@ -31,6 +32,7 @@ void poly1305_init(struct poly1305_desc_ctx *desc,
 	desc->s[3] = get_unaligned_le32(key + 28);
 	desc->buflen = 0;
 	poly1305_block_init(&desc->state, key);
+	kmsan_unpoison_memory(desc, sizeof(struct poly1305_desc_ctx));
 }
 EXPORT_SYMBOL(poly1305_init);
 
-- 
2.25.1

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+01fcd39a0d90cdb0e3df@syzkaller.appspotmail.com
Tested-by: syzbot+01fcd39a0d90cdb0e3df@syzkaller.appspotmail.com

Tested on:

commit:         6548d364 Merge tag 'cgroup-for-6.18-rc2-fixes' of git:..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1287a3e2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=bbd3e7f3c2e28265
dashboard link: https://syzkaller.appspot.com/bug?extid=01fcd39a0d90cdb0e3df
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1530cd42580000

Note: testing is done by a robot and is best-effort only.