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@xxxxxxxxxxxxxxxxxxxxxxxxx Link: https://lore.kernel.org/r/000000000000554b8205ffdea64e@xxxxxxxxxx/ Signed-off-by: David Howells <dhowells@xxxxxxxxxx> cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> cc: Paolo Abeni <pabeni@xxxxxxxxxx> cc: "David S. Miller" <davem@xxxxxxxxxxxxx> cc: Eric Dumazet <edumazet@xxxxxxxxxx> cc: Jakub Kicinski <kuba@xxxxxxxxxx> cc: linux-crypto@xxxxxxxxxxxxxxx cc: netdev@xxxxxxxxxxxxxxx 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);
