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Date: Fri, 07 Jul 2023 09:13:06 +0100
From: David Howells <dhowells@...hat.com>
To: Herbert Xu <herbert@...dor.apana.org.au>
Cc: dhowells@...hat.com,
syzbot <syzbot+e436ef6c393283630f64@...kaller.appspotmail.com>,
davem@...emloft.net, linux-crypto@...r.kernel.org,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [crypto?] KASAN: slab-out-of-bounds Write in crypto_sha3_final (2)
I'm pretty certain this is the same as:
https://syzkaller.appspot.com/bug?extid=689ec3afb1ef07b766b2
as I sometimes see the same trace when running the reproducer from there.
---
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
crypto: algif/hash: Fix race between MORE and non-MORE sends
The 'MSG_MORE' state of the previous sendmsg() is fetched without the
socket lock held, so two sendmsg calls can race. This can be seen with a
large sendfile() as that now does a series of sendmsg() calls, and if a
write() comes in on the same socket at an inopportune time, it can flip the
state.
Fix this by moving the fetch of ctx->more inside the socket lock.
Fixes: c662b043cdca ("crypto: af_alg/hash: Support MSG_SPLICE_PAGES")
Reported-by: syzbot+689ec3afb1ef07b766b2@...kaller.appspotmail.com
Link: https://lore.kernel.org/r/000000000000554b8205ffdea64e@google.com/
Signed-off-by: David Howells <dhowells@...hat.com>
cc: Herbert Xu <herbert@...dor.apana.org.au>
cc: Paolo Abeni <pabeni@...hat.com>
cc: "David S. Miller" <davem@...emloft.net>
cc: Eric Dumazet <edumazet@...gle.com>
cc: Jakub Kicinski <kuba@...nel.org>
cc: linux-crypto@...r.kernel.org
cc: netdev@...r.kernel.org
diff --git a/crypto/algif_hash.c b/crypto/algif_hash.c
index 0ab43e149f0e..82c44d4899b9 100644
--- a/crypto/algif_hash.c
+++ b/crypto/algif_hash.c
@@ -68,13 +68,15 @@ static int hash_sendmsg(struct socket *sock, struct msghdr *msg,
struct hash_ctx *ctx = ask->private;
ssize_t copied = 0;
size_t len, max_pages, npages;
- bool continuing = ctx->more, need_init = false;
+ bool continuing, need_init = false;
int err;
max_pages = min_t(size_t, ALG_MAX_PAGES,
DIV_ROUND_UP(sk->sk_sndbuf, PAGE_SIZE));
lock_sock(sk);
+ continuing = ctx->more;
+
if (!continuing) {
/* Discard a previous request that wasn't marked MSG_MORE. */
hash_free_result(sk, ctx);
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