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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <0000000000000cb2c305fdeb8e30@google.com> References: <0000000000000cb2c305fdeb8e30@google.com> To: syzbot Cc: dhowells@redhat.com, davem@davemloft.net, herbert@gondor.apana.org.au, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, pabeni@redhat.com, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [crypto?] general protection fault in cryptd_hash_export MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <1604627.1686754446.1@warthog.procyon.org.uk> Content-Transfer-Encoding: quoted-printable Date: Wed, 14 Jun 2023 15:54:06 +0100 Message-ID: <1604628.1686754446@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.g= it main crypto: af_alg/hash: Fix recvmsg() after sendmsg(MSG_MORE) = 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 u= p 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 mess= age is zero-length, it the data wrangling loop is skipped. = Fix this by always making a pass of the loop, even in the case that no= data is provided to the sendmsg(). = Fix also extract_iter_to_sg() to handle a zero-length iterator by retu= rning 0 immediately. = 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.co= m/ Signed-off-by: David Howells 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 diff --git a/crypto/algif_hash.c b/crypto/algif_hash.c index dfb048cefb60..1176533a55c9 100644 --- a/crypto/algif_hash.c +++ b/crypto/algif_hash.c @@ -83,26 +83,14 @@ static int hash_sendmsg(struct socket *sock, struct ms= ghdr *msg, = ctx->more =3D false; = - while (msg_data_left(msg)) { + do { ctx->sgl.sgt.sgl =3D ctx->sgl.sgl; ctx->sgl.sgt.nents =3D 0; ctx->sgl.sgt.orig_nents =3D 0; = err =3D -EIO; npages =3D iov_iter_npages(&msg->msg_iter, max_pages); - if (npages =3D=3D 0) - goto unlock_free; - - if (npages > ARRAY_SIZE(ctx->sgl.sgl)) { - err =3D -ENOMEM; - ctx->sgl.sgt.sgl =3D - 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); + sg_init_table(ctx->sgl.sgl, max_t(size_t, npages, 1)); = ctx->sgl.need_unpin =3D iov_iter_extract_will_pin(&msg->msg_iter); = @@ -111,7 +99,8 @@ static int hash_sendmsg(struct socket *sock, struct msg= hdr *msg, if (err < 0) goto unlock_free; len =3D err; - sg_mark_end(ctx->sgl.sgt.sgl + ctx->sgl.sgt.nents - 1); + if (len > 0) + sg_mark_end(ctx->sgl.sgt.sgl + ctx->sgl.sgt.nents - 1); = if (!msg_data_left(msg)) { err =3D hash_alloc_result(sk, ctx); @@ -148,7 +137,7 @@ static int hash_sendmsg(struct socket *sock, struct ms= ghdr *msg, = copied +=3D len; af_alg_free_sg(&ctx->sgl); - } + } while (msg_data_left(msg)); = ctx->more =3D msg->msg_flags & MSG_MORE; err =3D 0; diff --git a/lib/scatterlist.c b/lib/scatterlist.c index e97d7060329e..77a7b18ee751 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -1340,7 +1340,7 @@ ssize_t extract_iter_to_sg(struct iov_iter *iter, si= ze_t maxsize, struct sg_table *sgtable, unsigned int sg_max, iov_iter_extraction_t extraction_flags) { - if (maxsize =3D=3D 0) + if (!maxsize || !iter->count) return 0; = switch (iov_iter_type(iter)) {