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[76.217.55.94]) by smtp.gmail.com with ESMTPSA id x28sm12609592qtm.71.2021.07.23.11.36.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 Jul 2021 11:36:38 -0700 (PDT) From: Cong Wang To: netdev@vger.kernel.org Cc: Cong Wang , Eric Dumazet , John Fastabend , Daniel Borkmann , Jakub Sitnicki , Lorenz Bauer Subject: [Patch bpf-next] unix_bpf: fix a potential deadlock in unix_dgram_bpf_recvmsg() Date: Fri, 23 Jul 2021 11:36:30 -0700 Message-Id: <20210723183630.5088-1-xiyou.wangcong@gmail.com> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Cong Wang As Eric noticed, __unix_dgram_recvmsg() may acquire u->iolock too, so we have to release it before calling this function. Fixes: 9825d866ce0d ("af_unix: Implement unix_dgram_bpf_recvmsg()") Reported-by: Eric Dumazet Cc: John Fastabend Cc: Daniel Borkmann Cc: Jakub Sitnicki Cc: Lorenz Bauer Signed-off-by: Cong Wang Acked-by: Jakub Sitnicki Acked-by: John Fastabend --- net/unix/unix_bpf.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/net/unix/unix_bpf.c b/net/unix/unix_bpf.c index db0cda29fb2f..b07cb30e87b1 100644 --- a/net/unix/unix_bpf.c +++ b/net/unix/unix_bpf.c @@ -53,8 +53,9 @@ static int unix_dgram_bpf_recvmsg(struct sock *sk, struct msghdr *msg, mutex_lock(&u->iolock); if (!skb_queue_empty(&sk->sk_receive_queue) && sk_psock_queue_empty(psock)) { - ret = __unix_dgram_recvmsg(sk, msg, len, flags); - goto out; + mutex_unlock(&u->iolock); + sk_psock_put(sk, psock); + return __unix_dgram_recvmsg(sk, msg, len, flags); } msg_bytes_ready: @@ -68,13 +69,13 @@ static int unix_dgram_bpf_recvmsg(struct sock *sk, struct msghdr *msg, if (data) { if (!sk_psock_queue_empty(psock)) goto msg_bytes_ready; - ret = __unix_dgram_recvmsg(sk, msg, len, flags); - goto out; + mutex_unlock(&u->iolock); + sk_psock_put(sk, psock); + return __unix_dgram_recvmsg(sk, msg, len, flags); } copied = -EAGAIN; } ret = copied; -out: mutex_unlock(&u->iolock); sk_psock_put(sk, psock); return ret;