diff options
| author | Hou Tao <houtao1@huawei.com> | 2017-11-01 15:42:36 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-11-30 08:37:20 +0000 |
| commit | 4e82464aa4a398207e2ecbc4877c82319ecdbafa (patch) | |
| tree | 470f34f15b5ecbcc74189d699dfb9c1be1b6e6ac /drivers/md | |
| parent | 36c4819abc92e6cb22de81568407a92cdb8e9363 (diff) | |
dm: fix race between dm_get_from_kobject() and __dm_destroy()
commit b9a41d21dceadf8104812626ef85dc56ee8a60ed upstream.
The following BUG_ON was hit when testing repeat creation and removal of
DM devices:
kernel BUG at drivers/md/dm.c:2919!
CPU: 7 PID: 750 Comm: systemd-udevd Not tainted 4.1.44
Call Trace:
[<ffffffff81649e8b>] dm_get_from_kobject+0x34/0x3a
[<ffffffff81650ef1>] dm_attr_show+0x2b/0x5e
[<ffffffff817b46d1>] ? mutex_lock+0x26/0x44
[<ffffffff811df7f5>] sysfs_kf_seq_show+0x83/0xcf
[<ffffffff811de257>] kernfs_seq_show+0x23/0x25
[<ffffffff81199118>] seq_read+0x16f/0x325
[<ffffffff811de994>] kernfs_fop_read+0x3a/0x13f
[<ffffffff8117b625>] __vfs_read+0x26/0x9d
[<ffffffff8130eb59>] ? security_file_permission+0x3c/0x44
[<ffffffff8117bdb8>] ? rw_verify_area+0x83/0xd9
[<ffffffff8117be9d>] vfs_read+0x8f/0xcf
[<ffffffff81193e34>] ? __fdget_pos+0x12/0x41
[<ffffffff8117c686>] SyS_read+0x4b/0x76
[<ffffffff817b606e>] system_call_fastpath+0x12/0x71
The bug can be easily triggered, if an extra delay (e.g. 10ms) is added
between the test of DMF_FREEING & DMF_DELETING and dm_get() in
dm_get_from_kobject().
To fix it, we need to ensure the test of DMF_FREEING & DMF_DELETING and
dm_get() are done in an atomic way, so _minor_lock is used.
The other callers of dm_get() have also been checked to be OK: some
callers invoke dm_get() under _minor_lock, some callers invoke it under
_hash_lock, and dm_start_request() invoke it after increasing
md->open_count.
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/md')
| -rw-r--r-- | drivers/md/dm.c | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 320eb3c4bb6b..9ec6948e3b8b 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -3507,11 +3507,15 @@ struct mapped_device *dm_get_from_kobject(struct kobject *kobj) md = container_of(kobj, struct mapped_device, kobj_holder.kobj); - if (test_bit(DMF_FREEING, &md->flags) || - dm_deleting_md(md)) - return NULL; - + spin_lock(&_minor_lock); + if (test_bit(DMF_FREEING, &md->flags) || dm_deleting_md(md)) { + md = NULL; + goto out; + } dm_get(md); +out: + spin_unlock(&_minor_lock); + return md; } |