This is a note to let you know that I've just added the patch titled

crypto: af_alg - wait for data at beginning of recvmsg

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: crypto-af_alg-wait-for-data-at-beginning-of-recvmsg.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 11edb555966ed2c66c533d17c604f9d7e580a829 Mon Sep 17 00:00:00 2001

From: Stephan Mueller smueller@chronox.de Date: Wed, 29 Nov 2017 12:02:23 +0100 Subject: crypto: af_alg - wait for data at beginning of recvmsg

From: Stephan Mueller smueller@chronox.de

commit 11edb555966ed2c66c533d17c604f9d7e580a829 upstream.

The wait for data is a non-atomic operation that can sleep and therefore potentially release the socket lock. The release of the socket lock allows another thread to modify the context data structure. The waiting operation for new data therefore must be called at the beginning of recvmsg. This prevents a race condition where checks of the members of the context data structure are performed by recvmsg while there is a potential for modification of these values.

Fixes: e870456d8e7c ("crypto: algif_skcipher - overhaul memory management") Fixes: d887c52d6ae4 ("crypto: algif_aead - overhaul memory management") Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: Stephan Mueller smueller@chronox.de Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- crypto/af_alg.c | 6 ------ crypto/algif_aead.c | 6 ++++++ crypto/algif_skcipher.c | 6 ++++++ 3 files changed, 12 insertions(+), 6 deletions(-)

--- a/crypto/af_alg.c +++ b/crypto/af_alg.c @@ -1165,12 +1165,6 @@ int af_alg_get_rsgl(struct sock *sk, str if (!af_alg_readable(sk)) break;

- if (!ctx->used) { - err = af_alg_wait_for_data(sk, flags); - if (err) - return err; - } - seglen = min_t(size_t, (maxsize - len), msg_data_left(msg));

--- a/crypto/algif_aead.c +++ b/crypto/algif_aead.c @@ -111,6 +111,12 @@ static int _aead_recvmsg(struct socket * size_t usedpages = 0; /* [in] RX bufs to be used from user */ size_t processed = 0; /* [in] TX bufs to be consumed */

+ if (!ctx->used) { + err = af_alg_wait_for_data(sk, flags); + if (err) + return err; + } + /* * Data length provided by caller via sendmsg/sendpage that has not * yet been processed. --- a/crypto/algif_skcipher.c +++ b/crypto/algif_skcipher.c @@ -72,6 +72,12 @@ static int _skcipher_recvmsg(struct sock int err = 0; size_t len = 0;

+ if (!ctx->used) { + err = af_alg_wait_for_data(sk, flags); + if (err) + return err; + } + /* Allocate cipher request for current operation. */ areq = af_alg_alloc_areq(sk, sizeof(struct af_alg_async_req) + crypto_skcipher_reqsize(tfm));

Patches currently in stable-queue which might be from smueller@chronox.de are

queue-4.14/crypto-af_alg-wait-for-data-at-beginning-of-recvmsg.patch queue-4.14/crypto-af_alg-fix-race-accessing-cipher-request.patch