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crypto: af_alg/hash: Fix recvmsg() after sendmsg(MSG_MORE)

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If an AF_ALG socket bound to a hashing algorithm is sent a zero-length
message with MSG_MORE set and then recvmsg() is called without first
sending another message without MSG_MORE set to end the operation, an oops
will occur because the crypto context and result doesn't now get set up in
advance because hash_sendmsg() now defers that as long as possible in the
hope that it can use crypto_ahash_digest() - and then because the message
is zero-length, it the data wrangling loop is skipped.

Fix this by handling zero-length sends at the top of the hash_sendmsg()
function.  If we're not continuing the previous sendmsg(), then just ignore
the send (hash_recvmsg() will invent something when called); if we are
continuing, then we finalise the request at this point if MSG_MORE is not
set to get any error here, otherwise the send is of no effect and can be
ignored.

Whilst we're at it, remove the code to create a kvmalloc'd scatterlist if
we get more than ALG_MAX_PAGES - this shouldn't happen.

Fixes: c662b043cd ("crypto: af_alg/hash: Support MSG_SPLICE_PAGES")
Reported-by: syzbot+13a08c0bf4d212766c3c@syzkaller.appspotmail.com
Link: https://lore.kernel.org/r/000000000000b928f705fdeb873a@google.com/
Reported-by: syzbot+14234ccf6d0ef629ec1a@syzkaller.appspotmail.com
Link: https://lore.kernel.org/r/000000000000c047db05fdeb8790@google.com/
Reported-by: syzbot+4e2e47f32607d0f72d43@syzkaller.appspotmail.com
Link: https://lore.kernel.org/r/000000000000bcca3205fdeb87fb@google.com/
Reported-by: syzbot+472626bb5e7c59fb768f@syzkaller.appspotmail.com
Link: https://lore.kernel.org/r/000000000000b55d8805fdeb8385@google.com/
Signed-off-by: David Howells <dhowells@redhat.com>
Reported-and-tested-by: syzbot+6efc50cc1f8d718d6cb7@syzkaller.appspotmail.com
cc: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Link: https://lore.kernel.org/r/427646.1686913832@warthog.procyon.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
David Howells 2023-06-16 12:10:32 +01:00 committed by Jakub Kicinski
parent 462a3daad6
commit b6d972f689
1 changed files with 25 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

38
crypto/algif_hash.c
View File

@ -76,13 +76,30 @@ static int hash_sendmsg(struct socket *sock, struct msghdr *msg,
lock_sock(sk);
if (!continuing) {
if ((msg->msg_flags & MSG_MORE))
hash_free_result(sk, ctx);
/* Discard a previous request that wasn't marked MSG_MORE. */
hash_free_result(sk, ctx);
if (!msg_data_left(msg))
goto done; /* Zero-length; don't start new req */
need_init = true;
} else if (!msg_data_left(msg)) {
/*
* No data - finalise the prev req if MSG_MORE so any error
* comes out here.
*/
if (!(msg->msg_flags & MSG_MORE)) {
err = hash_alloc_result(sk, ctx);
if (err)
goto unlock_free;
ahash_request_set_crypt(&ctx->req, NULL,
ctx->result, 0);
err = crypto_wait_req(crypto_ahash_final(&ctx->req),
&ctx->wait);
if (err)
goto unlock_free;
}
goto done_more;
}
ctx->more = false;
while (msg_data_left(msg)) {
ctx->sgl.sgt.sgl = ctx->sgl.sgl;
ctx->sgl.sgt.nents = 0;
@ -93,15 +110,6 @@ static int hash_sendmsg(struct socket *sock, struct msghdr *msg,
if (npages == 0)
goto unlock_free;
if (npages > ARRAY_SIZE(ctx->sgl.sgl)) {
err = -ENOMEM;
ctx->sgl.sgt.sgl =
kvmalloc(array_size(npages,
sizeof(*ctx->sgl.sgt.sgl)),
GFP_KERNEL);
if (!ctx->sgl.sgt.sgl)
goto unlock_free;
}
sg_init_table(ctx->sgl.sgl, npages);
ctx->sgl.need_unpin = iov_iter_extract_will_pin(&msg->msg_iter);
@ -150,7 +158,9 @@ static int hash_sendmsg(struct socket *sock, struct msghdr *msg,
af_alg_free_sg(&ctx->sgl);
}
done_more:
ctx->more = msg->msg_flags & MSG_MORE;
done:
err = 0;
unlock:
release_sock(sk);
@ -158,6 +168,8 @@ unlock:
unlock_free:
af_alg_free_sg(&ctx->sgl);
hash_free_result(sk, ctx);
ctx->more = false;
goto unlock;
}