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Message-Id: <20171227164615.573985766@linuxfoundation.org> Date: Wed, 27 Dec 2017 17:46:10 +0100 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, syzbot <syzkaller@...glegroups.com>, Stephan Mueller <smueller@...onox.de>, Herbert Xu <herbert@...dor.apana.org.au> Subject: [PATCH 4.14 37/74] crypto: af_alg - wait for data at beginning of recvmsg 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Stephan Mueller <smueller@...onox.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@...glegroups.com> Signed-off-by: Stephan Mueller <smueller@...onox.de> Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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));
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