On 07/29/2016 04:55 AM, Vegard Nossum wrote:
On 05/30/2016 02:58 PM, Markus Pargmann wrote:
Hi,
On Friday 27 May 2016 12:59:35 Vegard Nossum wrote:
Quentin ran into this bug:
WARNING: CPU: 64 PID: 10085 at fs/sysfs/dir.c:31
sysfs_warn_dup+0x65/0x80
[...]
It seems fairly obvious that device_create_file() is not being protected
from being run concurrently on the same nbd.
Quentin found the following relevant commits:
1a2ad21 nbd: add locking to nbd_ioctl
90b8f28 [PATCH] end of methods switch: remove the old ones
d4430d6 [PATCH] beginning of methods conversion
08f8585 [PATCH] move block_device_operations to blkdev.h
It would seem that the race was introduced in the process of moving nbd
from BKL to unlocked ioctls.
By setting nbd->task_recv while the mutex is held, we can prevent other
processes from running concurrently (since nbd->task_recv is also
checked
while the mutex is held).
Reported-and-tested-by: Quentin Casasnovas
<quentin.casasnovas@xxxxxxxxxx>
Cc: Markus Pargmann <mpa@xxxxxxxxxxxxxx>
Cc: Paul Clements <paul.clements@xxxxxxxxxxxx>
Cc: Pavel Machek <pavel@xxxxxxx>
Cc: Jens Axboe <axboe@xxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
Thanks, applied.
Best Regards,
Markus
Hi,
I didn't see this patch in the batch that went into 4.8, so I'm just
following up to make sure it doesn't get lost.
Moreover, it should also probably go into stable.
I have applied it for 4.8.
--
Jens Axboe
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