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af_unix: conditionally use freezable blocking calls in read 

Commit 2b15af6f95 ("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 2b514574f7
("net: af_unix: implement splice for stream af_unix sockets") breaks
the strong requirement for a freezable sleep, according to
commit 0f9548ca1091:

    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: 2b514574f7 ("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>
steinar/wifi_calib_4_9_kernel
WANG Cong 2016-11-17 15:55:26 -08:00 committed by David S. Miller
parent 0e2d1af399
commit 06a77b07e3
1 changed files with 11 additions and 6 deletions
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17
net/unix/af_unix.c
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@ -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);
timeo = freezable_schedule_timeout(timeo);
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)