af_unix: conditionally use freezable blocking calls in read (06a77b07) · Commits · 戴 / test

Commit ("af_unix: use freezable blocking calls in read") converts schedule_timeout() to its freezable version, it was probably correct at that time, but later, commit ("net: af_unix: implement splice for stream af_unix sockets") breaks the strong requirement for a freezable sleep, according to commit : We shouldn't try_to_freeze if locks are held. Holding a lock can cause a deadlock if the lock is later acquired in the suspend or hibernate path (e.g. by dpm). Holding a lock can also cause a deadlock in the case of cgroup_freezer if a lock is held inside a frozen cgroup that is later acquired by a process outside that group. The pipe_lock is still held at that point. So use freezable version only for the recvmsg call path, avoid impact for Android. Fixes: ("net: af_unix: implement splice for stream af_unix sockets") Reported-by:

Dmitry Vyukov <dvyukov@google.com> Cc: Tejun Heo <tj@kernel.org> Cc: Colin Cross <ccross@android.com> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: Hannes Frederic Sowa <hannes@stressinduktion.org> Signed-off-by:

Cong Wang <xiyou.wangcong@gmail.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/unix/af_unix.c

+11 −6

Original line number	Diff line number	Diff line
		@@ -2199,7 +2199,8 @@ out:
		* Sleep until more data has arrived. But check for races..
		*/
		static long unix_stream_data_wait(struct sock *sk, long timeo,
		struct sk_buff *last, unsigned int last_len)
		struct sk_buff *last, unsigned int last_len,
		bool freezable)
		{
		struct sk_buff *tail;
		DEFINE_WAIT(wait);
		@@ -2220,7 +2221,10 @@ static long unix_stream_data_wait(struct sock *sk, long timeo,

		sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
		unix_state_unlock(sk);
		if (freezable)
		timeo = freezable_schedule_timeout(timeo);
		else
		timeo = schedule_timeout(timeo);
		unix_state_lock(sk);

		if (sock_flag(sk, SOCK_DEAD))
		@@ -2250,7 +2254,8 @@ struct unix_stream_read_state {
		unsigned int splice_flags;
		};

		static int unix_stream_read_generic(struct unix_stream_read_state *state)
		static int unix_stream_read_generic(struct unix_stream_read_state *state,
		bool freezable)
		{
		struct scm_cookie scm;
		struct socket *sock = state->socket;
		@@ -2330,7 +2335,7 @@ again:
		mutex_unlock(&u->iolock);

		timeo = unix_stream_data_wait(sk, timeo, last,
		last_len);
		last_len, freezable);

		if (signal_pending(current)) {
		err = sock_intr_errno(timeo);
		@@ -2472,7 +2477,7 @@ static int unix_stream_recvmsg(struct socket sock, struct msghdr msg,
		.flags = flags
		};

		return unix_stream_read_generic(&state);
		return unix_stream_read_generic(&state, true);
		}

		static int unix_stream_splice_actor(struct sk_buff *skb,
		@@ -2503,7 +2508,7 @@ static ssize_t unix_stream_splice_read(struct socket sock, loff_t ppos,
		flags & SPLICE_F_NONBLOCK)
		state.flags = MSG_DONTWAIT;

		return unix_stream_read_generic(&state);
		return unix_stream_read_generic(&state, false);
		}

		static int unix_shutdown(struct socket *sock, int mode)

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