Re: [syzbot] [crypto?] KASAN: slab-out-of-bounds Write in crypto_sha3_final (2)

[syzbot]

> 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

This crash does not have a reproducer. I cannot test it.

>
>     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);
>