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btrfs: fix crash when tracepoint arguments are freed by wq callbacks

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Enabling btrfs tracepoints leads to instant crash, as reported. The wq
callbacks could free the memory and the tracepoints started to
dereference the members to get to fs_info.

The proposed fix https://marc.info/?l=linux-btrfs&m=148172436722606&w=2
removed the tracepoints but we could preserve them by passing only the
required data in a safe way.

Fixes: bc074524e1 ("btrfs: prefix fsid to all trace events")
CC: stable@vger.kernel.org # 4.8+
Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2017-01-06 14:12:51 +01:00
parent 2939e1a86f
commit ac0c7cf8be
2 changed files with 24 additions and 13 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

15
fs/btrfs/async-thread.c
View file

@ -273,6 +273,8 @@ static void run_ordered_work(struct __btrfs_workqueue *wq)
unsigned long flags;
while (1) {
void *wtag;
spin_lock_irqsave(lock, flags);
if (list_empty(list))
break;
@ -299,11 +301,13 @@ static void run_ordered_work(struct __btrfs_workqueue *wq)
spin_unlock_irqrestore(lock, flags);
/*
* we don't want to call the ordered free functions
* with the lock held though
* We don't want to call the ordered free functions with the
* lock held though. Save the work as tag for the trace event,
* because the callback could free the structure.
*/
wtag = work;
work->ordered_free(work);
trace_btrfs_all_work_done(work);
trace_btrfs_all_work_done(wq->fs_info, wtag);
}
spin_unlock_irqrestore(lock, flags);
}
@ -311,6 +315,7 @@ static void run_ordered_work(struct __btrfs_workqueue *wq)
static void normal_work_helper(struct btrfs_work *work)
{
struct __btrfs_workqueue *wq;
void *wtag;
int need_order = 0;
/*
@ -324,6 +329,8 @@ static void normal_work_helper(struct btrfs_work *work)
if (work->ordered_func)
need_order = 1;
wq = work->wq;
/* Safe for tracepoints in case work gets freed by the callback */
wtag = work;
trace_btrfs_work_sched(work);
thresh_exec_hook(wq);
@ -333,7 +340,7 @@ static void normal_work_helper(struct btrfs_work *work)
run_ordered_work(wq);
}
if (!need_order)
trace_btrfs_all_work_done(work);
trace_btrfs_all_work_done(wq->fs_info, wtag);
}
void btrfs_init_work(struct btrfs_work *work, btrfs_work_func_t uniq_func,

22
include/trace/events/btrfs.h
View file

@ -1157,22 +1157,26 @@ DECLARE_EVENT_CLASS(btrfs__work,
__entry->func, __entry->ordered_func, __entry->ordered_free)
);
/* For situiations that the work is freed */
/*
* For situiations when the work is freed, we pass fs_info and a tag that that
* matches address of the work structure so it can be paired with the
* scheduling event.
*/
DECLARE_EVENT_CLASS(btrfs__work__done,
TP_PROTO(struct btrfs_work *work),
TP_PROTO(struct btrfs_fs_info *fs_info, void *wtag),
TP_ARGS(work),
TP_ARGS(fs_info, wtag),
TP_STRUCT__entry_btrfs(
__field( void *, work )
__field( void *, wtag )
),
TP_fast_assign_btrfs(btrfs_work_owner(work),
__entry->work = work;
TP_fast_assign_btrfs(fs_info,
__entry->wtag = wtag;
),
TP_printk_btrfs("work->%p", __entry->work)
TP_printk_btrfs("work->%p", __entry->wtag)
);
DEFINE_EVENT(btrfs__work, btrfs_work_queued,
@ -1191,9 +1195,9 @@ DEFINE_EVENT(btrfs__work, btrfs_work_sched,
DEFINE_EVENT(btrfs__work__done, btrfs_all_work_done,
TP_PROTO(struct btrfs_work *work),
TP_PROTO(struct btrfs_fs_info *fs_info, void *wtag),
TP_ARGS(work)
TP_ARGS(fs_info, wtag)
);
DEFINE_EVENT(btrfs__work, btrfs_ordered_sched,