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 2b514574f7e8
("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: 2b514574f7e8 ("net: af_unix: implement splice for stream af_unix
sockets")
Reported-by: Dmitry Vyukov <dvyu...@google.com>
Cc: Tejun Heo <t...@kernel.org>
Cc: Colin Cross <ccr...@android.com>
Cc: Rafael J. Wysocki <rafael.j.wyso...@intel.com>
Cc: Hannes Frederic Sowa <han...@stressinduktion.org>
Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
---
net/unix/af_unix.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 5d1c14a..2358f26 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2199,7 +2199,8 @@ static int unix_dgram_recvmsg(struct socket *sock, struct
msghdr *msg,
* 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 @@ static int unix_stream_read_generic(struct
unix_stream_read_state *state)
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)
--
2.1.0
