| Message ID | 427646.1686913832@warthog.procyon.org.uk |
|---|---|
| State | Accepted |
| Commit | b6d972f6898308fbe7e693bf8d44ebfdb1cd2dc4 |
| Headers | show |
| Series | [net-next,v2] crypto: af_alg/hash: Fix recvmsg() after sendmsg(MSG_MORE) | expand |
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 <dhowells@redhat.com> > Reported-and-tested-by: syzbot+6efc50cc1f8d718d6cb7@syzkaller.appspotmail.com > cc: Herbert Xu <herbert@gondor.apana.org.au> > cc: "David S. Miller" <davem@davemloft.net> > cc: Eric Dumazet <edumazet@google.com> > cc: Jakub Kicinski <kuba@kernel.org> > cc: Paolo Abeni <pabeni@redhat.com> > cc: Jens Axboe <axboe@kernel.dk> > cc: Matthew Wilcox <willy@infradead.org> > 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,
Herbert Xu <herbert@gondor.apana.org.au> wrote: > > + 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. Not so. hash_recvmsg() will call crypto_ahash_init() first because ctx->more is false (hence why we came down this branch in hash_sendmsg()) and the result was released on the previous line (which you're objecting to). If it goes to the "done" label, it will skip setting ctx->more to true if MSG_MORE is passed. However, given you want sendmsg() to do the init->digest cycle on zero length data, I think we should revert to the previous version of the patch that makes a pass of the loop even with no data. David
On Tue, Jun 20, 2023 at 08:42:15AM +0100, David Howells wrote: > > Not so. hash_recvmsg() will call crypto_ahash_init() first because ctx->more > is false (hence why we came down this branch in hash_sendmsg()) and the result > was released on the previous line (which you're objecting to). If it goes to > the "done" label, it will skip setting ctx->more to true if MSG_MORE is > passed. I see, yes it should work. > However, given you want sendmsg() to do the init->digest cycle on zero length > data, I think we should revert to the previous version of the patch that makes > a pass of the loop even with no data. Let's get this fixed ASAP and we can refine it later. Acked-by: Herbert Xu <herbert@gondor.apana.org.au> Thanks,
Herbert Xu <herbert@gondor.apana.org.au> wrote: > > However, given you want sendmsg() to do the init->digest cycle on zero length > > data, I think we should revert to the previous version of the patch that makes > > a pass of the loop even with no data. > > Let's get this fixed ASAP and we can refine it later. > > Acked-by: Herbert Xu <herbert@gondor.apana.org.au> Um. Is that against this patch or the old version? David
On Tue, Jun 20, 2023 at 09:31:56AM +0100, David Howells wrote: > Herbert Xu <herbert@gondor.apana.org.au> wrote: > > > > However, given you want sendmsg() to do the init->digest cycle on zero length > > > data, I think we should revert to the previous version of the patch that makes > > > a pass of the loop even with no data. > > > > Let's get this fixed ASAP and we can refine it later. > > > > Acked-by: Herbert Xu <herbert@gondor.apana.org.au> > > Um. Is that against this patch or the old version? This is against v2 which started this thread. Cheers,
Hello: This patch was applied to netdev/net-next.git (main) by Jakub Kicinski <kuba@kernel.org>: On Fri, 16 Jun 2023 12:10:32 +0100 you 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. > > [...] Here is the summary with links: - [net-next,v2] crypto: af_alg/hash: Fix recvmsg() after sendmsg(MSG_MORE) https://git.kernel.org/netdev/net-next/c/b6d972f68983 You are awesome, thank you!
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); + 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 @@ static int hash_sendmsg(struct socket *sock, struct msghdr *msg, unlock_free: af_alg_free_sg(&ctx->sgl); + hash_free_result(sk, ctx); + ctx->more = false; goto unlock; }
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 <dhowells@redhat.com> Reported-and-tested-by: syzbot+6efc50cc1f8d718d6cb7@syzkaller.appspotmail.com cc: Herbert Xu <herbert@gondor.apana.org.au> cc: "David S. Miller" <davem@davemloft.net> cc: Eric Dumazet <edumazet@google.com> cc: Jakub Kicinski <kuba@kernel.org> cc: Paolo Abeni <pabeni@redhat.com> cc: Jens Axboe <axboe@kernel.dk> cc: Matthew Wilcox <willy@infradead.org> cc: linux-crypto@vger.kernel.org cc: netdev@vger.kernel.org --- crypto/algif_hash.c | 38 +++++++++++++++++++++++++------------- 1 file changed, 25 insertions(+), 13 deletions(-)