This is a note to let you know that I've just added the patch titled
rfkill: fix rfkill_fop_read wait_event usage
to the 3.10-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:
rfkill-fix-rfkill_fop_read-wait_event-usage.patch
and it can be found in the queue-3.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 6736fde9672ff6717ac576e9bba2fd5f3dfec822 Mon Sep 17 00:00:00 2001
From: Johannes Berg <johannes.berg@xxxxxxxxx>
Date: Tue, 26 Jan 2016 11:29:03 +0100
Subject: rfkill: fix rfkill_fop_read wait_event usage
From: Johannes Berg <johannes.berg@xxxxxxxxx>
commit 6736fde9672ff6717ac576e9bba2fd5f3dfec822 upstream.
The code within wait_event_interruptible() is called with
!TASK_RUNNING, so mustn't call any functions that can sleep,
like mutex_lock().
Since we re-check the list_empty() in a loop after the wait,
it's safe to simply use list_empty() without locking.
This bug has existed forever, but was only discovered now
because all userspace implementations, including the default
'rfkill' tool, use poll() or select() to get a readable fd
before attempting to read.
Fixes: c64fb01627e24 ("rfkill: create useful userspace interface")
Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/rfkill/core.c | 16 ++++------------
1 file changed, 4 insertions(+), 12 deletions(-)
--- a/net/rfkill/core.c
+++ b/net/rfkill/core.c
@@ -1088,17 +1088,6 @@ static unsigned int rfkill_fop_poll(stru
return res;
}
-static bool rfkill_readable(struct rfkill_data *data)
-{
- bool r;
-
- mutex_lock(&data->mtx);
- r = !list_empty(&data->events);
- mutex_unlock(&data->mtx);
-
- return r;
-}
-
static ssize_t rfkill_fop_read(struct file *file, char __user *buf,
size_t count, loff_t *pos)
{
@@ -1115,8 +1104,11 @@ static ssize_t rfkill_fop_read(struct fi
goto out;
}
mutex_unlock(&data->mtx);
+ /* since we re-check and it just compares pointers,
+ * using !list_empty() without locking isn't a problem
+ */
ret = wait_event_interruptible(data->read_wait,
- rfkill_readable(data));
+ !list_empty(&data->events));
mutex_lock(&data->mtx);
if (ret)
Patches currently in stable-queue which might be from johannes.berg@xxxxxxxxx are
queue-3.10/rfkill-copy-the-name-into-the-rfkill-struct.patch
queue-3.10/mac80211-mesh-fix-call_rcu-usage.patch
queue-3.10/rfkill-fix-rfkill_fop_read-wait_event-usage.patch
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