From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0CFC3EB64D7 for ; Tue, 20 Jun 2023 04:51:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230084AbjFTEvg (ORCPT ); Tue, 20 Jun 2023 00:51:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46828 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229522AbjFTEvb (ORCPT ); Tue, 20 Jun 2023 00:51:31 -0400 Received: from 167-179-156-38.a7b39c.syd.nbn.aussiebb.net (167-179-156-38.a7b39c.syd.nbn.aussiebb.net [167.179.156.38]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 413EF10D2; Mon, 19 Jun 2023 21:51:30 -0700 (PDT) Received: from loth.rohan.me.apana.org.au ([192.168.167.2]) by formenos.hmeau.com with smtp (Exim 4.94.2 #2 (Debian)) id 1qBTKe-004xnx-6L; Tue, 20 Jun 2023 12:51:09 +0800 Received: by loth.rohan.me.apana.org.au (sSMTP sendmail emulation); Tue, 20 Jun 2023 12:51:08 +0800 Date: Tue, 20 Jun 2023 12:51:08 +0800 From: Herbert Xu To: David Howells Cc: netdev@vger.kernel.org, syzbot+13a08c0bf4d212766c3c@syzkaller.appspotmail.com, syzbot+14234ccf6d0ef629ec1a@syzkaller.appspotmail.com, syzbot+4e2e47f32607d0f72d43@syzkaller.appspotmail.com, syzbot+472626bb5e7c59fb768f@syzkaller.appspotmail.com, "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Jens Axboe , Matthew Wilcox , linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next v2] crypto: af_alg/hash: Fix recvmsg() after sendmsg(MSG_MORE) Message-ID: References: <427646.1686913832@warthog.procyon.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <427646.1686913832@warthog.procyon.org.uk> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 16, 2023 at 12:10:32PM +0100, David Howells wrote: > 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: c662b043cdca ("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 > Reported-and-tested-by: syzbot+6efc50cc1f8d718d6cb7@syzkaller.appspotmail.com > cc: Herbert Xu > cc: "David S. Miller" > cc: Eric Dumazet > cc: Jakub Kicinski > cc: Paolo Abeni > cc: Jens Axboe > cc: Matthew Wilcox > cc: linux-crypto@vger.kernel.org > cc: netdev@vger.kernel.org > --- > crypto/algif_hash.c | 38 +++++++++++++++++++++++++------------- > 1 file changed, 25 insertions(+), 13 deletions(-) > > diff --git a/crypto/algif_hash.c b/crypto/algif_hash.c > index dfb048cefb60..0ab43e149f0e 100644 > --- a/crypto/algif_hash.c > +++ b/crypto/algif_hash.c > @@ -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); Please revert this change as I explained in the other message. > + if (!msg_data_left(msg)) > + goto done; /* Zero-length; don't start new req */ This is still broken in the case of a zero-length message with MSG_MORE set. Here you will short-circuit out without ever calling crypto_ahash_init. However, hash_recvmsg will directly call crypto_ahash_final on this, which is undefined. Cheers, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt