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author | Takashi Iwai <tiwai@suse.de> | 2016-11-30 15:54:08 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-11-30 16:32:52 -0800 |
commit | 529e71e16403830ae0d737a66c55c5f360f3576b (patch) | |
tree | 22a4e10af62d0ba5dd8694fffc88281b12bd467b /drivers | |
parent | 655548bf6271b212cd1e4c259da9dbe616348d38 (diff) | |
download | linux-stable-529e71e16403830ae0d737a66c55c5f360f3576b.tar.gz linux-stable-529e71e16403830ae0d737a66c55c5f360f3576b.tar.bz2 linux-stable-529e71e16403830ae0d737a66c55c5f360f3576b.zip |
zram: fix unbalanced idr management at hot removal
The zram hot removal code calls idr_remove() even when zram_remove()
returns an error (typically -EBUSY). This results in a leftover at the
device release, eventually leading to a crash when the module is
reloaded.
As described in the bug report below, the following procedure would
cause an Oops with zram:
- provision three zram devices via modprobe zram num_devices=3
- configure a size for each device
+ echo "1G" > /sys/block/$zram_name/disksize
- mkfs and mount zram0 only
- attempt to hot remove all three devices
+ echo 2 > /sys/class/zram-control/hot_remove
+ echo 1 > /sys/class/zram-control/hot_remove
+ echo 0 > /sys/class/zram-control/hot_remove
- zram0 removal fails with EBUSY, as expected
- unmount zram0
- try zram0 hot remove again
+ echo 0 > /sys/class/zram-control/hot_remove
- fails with ENODEV (unexpected)
- unload zram kernel module
+ completes successfully
- zram0 device node still exists
- attempt to mount /dev/zram0
+ mount command is killed
+ following BUG is encountered
BUG: unable to handle kernel paging request at ffffffffa0002ba0
IP: get_disk+0x16/0x50
Oops: 0000 [#1] SMP
CPU: 0 PID: 252 Comm: mount Not tainted 4.9.0-rc6 #176
Call Trace:
exact_lock+0xc/0x20
kobj_lookup+0xdc/0x160
get_gendisk+0x2f/0x110
__blkdev_get+0x10c/0x3c0
blkdev_get+0x19d/0x2e0
blkdev_open+0x56/0x70
do_dentry_open.isra.19+0x1ff/0x310
vfs_open+0x43/0x60
path_openat+0x2c9/0xf30
do_filp_open+0x79/0xd0
do_sys_open+0x114/0x1e0
SyS_open+0x19/0x20
entry_SYSCALL_64_fastpath+0x13/0x94
This patch adds the proper error check in hot_remove_store() not to call
idr_remove() unconditionally.
Fixes: 17ec4cd98578 ("zram: don't call idr_remove() from zram_remove()")
Bugzilla: https://bugzilla.opensuse.org/show_bug.cgi?id=1010970
Link: http://lkml.kernel.org/r/20161121132140.12683-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: David Disseldorp <ddiss@suse.de>
Reported-by: David Disseldorp <ddiss@suse.de>
Tested-by: David Disseldorp <ddiss@suse.de>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: <stable@vger.kernel.org> [4.4+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers')
-rw-r--r-- | drivers/block/zram/zram_drv.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 04365b17ee67..5163c8f918cb 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -1403,7 +1403,8 @@ static ssize_t hot_remove_store(struct class *class, zram = idr_find(&zram_index_idr, dev_id); if (zram) { ret = zram_remove(zram); - idr_remove(&zram_index_idr, dev_id); + if (!ret) + idr_remove(&zram_index_idr, dev_id); } else { ret = -ENODEV; } |