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authorTakashi Iwai <tiwai@suse.de>2016-11-30 15:54:08 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2016-11-30 16:32:52 -0800
commit529e71e16403830ae0d737a66c55c5f360f3576b (patch)
tree22a4e10af62d0ba5dd8694fffc88281b12bd467b /drivers/block/zram
parent655548bf6271b212cd1e4c259da9dbe616348d38 (diff)
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/block/zram')
-rw-r--r--drivers/block/zram/zram_drv.c3
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;
}