This is a note to let you know that I've just added the patch titled
af_unix: conditionally use freezable blocking calls in read
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
af_unix-conditionally-use-freezable-blocking-calls-in-read.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Thu Dec 8 07:18:57 CET 2016
From: WANG Cong <xiyou.wangcong@xxxxxxxxx>
Date: Thu, 17 Nov 2016 15:55:26 -0800
Subject: af_unix: conditionally use freezable blocking calls in read
From: WANG Cong <xiyou.wangcong@xxxxxxxxx>
[ Upstream commit 06a77b07e3b44aea2b3c0e64de420ea2cfdcbaa9 ]
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 <dvyukov@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Colin Cross <ccross@xxxxxxxxxxx>
Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Cc: Hannes Frederic Sowa <hannes@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Cong Wang <xiyou.wangcong@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/unix/af_unix.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2194,7 +2194,8 @@ 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);
@@ -2215,7 +2216,10 @@ static long unix_stream_data_wait(struct
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))
@@ -2245,7 +2249,8 @@ 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;
@@ -2324,7 +2329,7 @@ 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);
@@ -2466,7 +2471,7 @@ static int unix_stream_recvmsg(struct so
.flags = flags
};
- return unix_stream_read_generic(&state);
+ return unix_stream_read_generic(&state, true);
}
static ssize_t skb_unix_socket_splice(struct sock *sk,
@@ -2512,7 +2517,7 @@ static ssize_t unix_stream_splice_read(s
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)
Patches currently in stable-queue which might be from xiyou.wangcong@xxxxxxxxx are
queue-4.4/net-sched-respect-rcu-grace-period-on-cls-destruction.patch
queue-4.4/af_unix-conditionally-use-freezable-blocking-calls-in-read.patch
queue-4.4/netlink-call-cb-done-from-a-worker-thread.patch
queue-4.4/net-check-dead-netns-for-peernet2id_alloc.patch
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