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| author | Jan Kara <jack@suse.cz> | 2017-03-23 01:37:02 +0100 |
|---|---|---|
| committer | Jens Axboe <axboe@fb.com> | 2017-03-23 03:11:37 +0100 |
| commit | d01b2dcb441b14c3b860d3d16ecb9ed6ed4ba7fb (patch) | |
| tree | b667a449649255a01e52a4dbb8219e7a53af7b14 /block/genhd.c | |
| parent | kobject: Export kobject_get_unless_zero() (diff) | |
| download | linux-d01b2dcb441b14c3b860d3d16ecb9ed6ed4ba7fb.tar.xz linux-d01b2dcb441b14c3b860d3d16ecb9ed6ed4ba7fb.zip | |
block: Fix oops scsi_disk_get()
When device open races with device shutdown, we can get the following
oops in scsi_disk_get():
[11863.044351] general protection fault: 0000 [#1] SMP
[11863.045561] Modules linked in: scsi_debug xfs libcrc32c netconsole btrfs raid6_pq zlib_deflate lzo_compress xor [last unloaded: loop]
[11863.047853] CPU: 3 PID: 13042 Comm: hald-probe-stor Tainted: G W 4.10.0-rc2-xen+ #35
[11863.048030] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[11863.048030] task: ffff88007f438200 task.stack: ffffc90000fd0000
[11863.048030] RIP: 0010:scsi_disk_get+0x43/0x70
[11863.048030] RSP: 0018:ffffc90000fd3a08 EFLAGS: 00010202
[11863.048030] RAX: 6b6b6b6b6b6b6b6b RBX: ffff88007f56d000 RCX: 0000000000000000
[11863.048030] RDX: 0000000000000001 RSI: 0000000000000004 RDI: ffffffff81a8d880
[11863.048030] RBP: ffffc90000fd3a18 R08: 0000000000000000 R09: 0000000000000001
[11863.059217] R10: 0000000000000000 R11: 0000000000000000 R12: 00000000fffffffa
[11863.059217] R13: ffff880078872800 R14: ffff880070915540 R15: 000000000000001d
[11863.059217] FS: 00007f2611f71800(0000) GS:ffff88007f0c0000(0000) knlGS:0000000000000000
[11863.059217] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[11863.059217] CR2: 000000000060e048 CR3: 00000000778d4000 CR4: 00000000000006e0
[11863.059217] Call Trace:
[11863.059217] ? disk_get_part+0x22/0x1f0
[11863.059217] sd_open+0x39/0x130
[11863.059217] __blkdev_get+0x69/0x430
[11863.059217] ? bd_acquire+0x7f/0xc0
[11863.059217] ? bd_acquire+0x96/0xc0
[11863.059217] ? blkdev_get+0x350/0x350
[11863.059217] blkdev_get+0x126/0x350
[11863.059217] ? _raw_spin_unlock+0x2b/0x40
[11863.059217] ? bd_acquire+0x7f/0xc0
[11863.059217] ? blkdev_get+0x350/0x350
[11863.059217] blkdev_open+0x65/0x80
...
As you can see RAX value is already poisoned showing that gendisk we got
is already freed. The problem is that get_gendisk() looks up device
number in ext_devt_idr and then does get_disk() which does kobject_get()
on the disks kobject. However the disk gets removed from ext_devt_idr
only in disk_release() (through blk_free_devt()) at which moment it has
already 0 refcount and is already on its way to be freed. Indeed we've
got a warning from kobject_get() about 0 refcount shortly before the
oops.
We fix the problem by using kobject_get_unless_zero() in get_disk() so
that get_disk() cannot get reference on a disk that is already being
freed.
Tested-by: Lekshmi Pillai <lekshmicpillai@in.ibm.com>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block/genhd.c')
| -rw-r--r-- | block/genhd.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/block/genhd.c b/block/genhd.c index a9c516a8b37d..510aac1486cb 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -1352,7 +1352,7 @@ struct kobject *get_disk(struct gendisk *disk) owner = disk->fops->owner; if (owner && !try_module_get(owner)) return NULL; - kobj = kobject_get(&disk_to_dev(disk)->kobj); + kobj = kobject_get_unless_zero(&disk_to_dev(disk)->kobj); if (kobj == NULL) { module_put(owner); return NULL; |