crypto: af_alg - wait for data at beginning of recvmsg

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>

diff --git a/crypto/af_alg.c b/crypto/af_alg.c
index e181073ef64d24bef17bc182de8778e4bb24b075..6ec360213107fa24fe7e981e1562bc2220373775 100644 (file)
--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -1165,12 +1165,6 @@ int af_alg_get_rsgl(struct sock *sk, struct msghdr *msg, int flags,
                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));
 

diff --git a/crypto/algif_aead.c b/crypto/algif_aead.c
index 3d793bc2aa82c0d091cfab222f4363eaa5768341..ba07da8422c6d7334ee357d95b7f2402ac543840 100644 (file)
--- a/crypto/algif_aead.c
+++ b/crypto/algif_aead.c
@@ -111,6 +111,12 @@ static int _aead_recvmsg(struct socket *sock, struct msghdr *msg,
        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.

diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c
index 30ee2a8e8f42929b0a2eb92b370ec3fdac03eb53..3f4458f08293c8998d38c369b2ab2b8257126a85 100644 (file)
--- a/crypto/algif_skcipher.c
+++ b/crypto/algif_skcipher.c
@@ -72,6 +72,12 @@ static int _skcipher_recvmsg(struct socket *sock, struct msghdr *msg,
        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));