From 0b7ec177b589842c0abf9e91459c83ba28d32452 Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 7 Jul 2023 10:12:38 +0100 Subject: [PATCH] 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@syzkaller.appspotmail.com Link: https://lore.kernel.org/r/000000000000554b8205ffdea64e@google.com/ Signed-off-by: David Howells Tested-by: syzbot+689ec3afb1ef07b766b2@syzkaller.appspotmail.com cc: Herbert Xu cc: Paolo Abeni cc: "David S. Miller" cc: Eric Dumazet cc: Jakub Kicinski cc: linux-crypto@vger.kernel.org cc: netdev@vger.kernel.org Signed-off-by: Herbert Xu --- crypto/algif_hash.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/crypto/algif_hash.c b/crypto/algif_hash.c index 0ab43e1..82c44d4 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); -- 2.7.4