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Sasha Levin 0ca3729102 zram: fix race between backing_dev_show and backing_dev_store 
[ Upstream commit f7daefe423 ]

CPU0:				       CPU1:
backing_dev_show		       backing_dev_store
    ......				   ......
    file = zram->backing_dev;
    down_read(&zram->init_lock);	   down_read(&zram->init_init_lock)
    file_path(file, ...);		   zram->backing_dev = backing_dev;
    up_read(&zram->init_lock);		   up_read(&zram->init_lock);

gets the value of zram->backing_dev too early in backing_dev_show, which
resultin the value being NULL at the beginning, and not NULL later.

backtrace:
  d_path+0xcc/0x174
  file_path+0x10/0x18
  backing_dev_show+0x40/0xb4
  dev_attr_show+0x20/0x54
  sysfs_kf_seq_show+0x9c/0x10c
  kernfs_seq_show+0x28/0x30
  seq_read+0x184/0x488
  kernfs_fop_read+0x5c/0x1a4
  __vfs_read+0x44/0x128
  vfs_read+0xa0/0x138
  SyS_read+0x54/0xb4

Link: http://lkml.kernel.org/r/1571046839-16814-1-git-send-email-chenwandun@huawei.com
Signed-off-by: Chenwandun <chenwandun@huawei.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: <stable@vger.kernel.org>	[4.14+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2019-11-06 13:05:10 +01:00
..
aoe drivers/block/aoe/aoedev: NULL check is not needed for mempool_destroy 2018-08-08 09:17:20 -06:00
drbd drbd: dynamically allocate shash descriptor 2019-08-16 10:12:48 +02:00
mtip32xx Merge branch 'ida-4.19' of git://git.infradead.org/users/willy/linux-dax 2018-08-26 11:48:42 -07:00
paride block: paride: pd: mark expected switch fall-throughs 2018-08-09 10:17:38 -06:00
rsxx Merge branch 'ida-4.19' of git://git.infradead.org/users/willy/linux-dax 2018-08-26 11:48:42 -07:00
xen-blkback xen/blkback: fix memory leaks 2019-09-06 10:21:57 +02:00
zram zram: fix race between backing_dev_show and backing_dev_store 2019-11-06 13:05:10 +01:00
amiflop.c genhd: Rename get_disk() to get_disk_and_module() 2018-02-26 09:48:42 -07:00
ataflop.c ataflop: fix error handling during setup 2018-11-13 11:08:20 -08:00
brd.c brd: re-enable __GFP_HIGHMEM in brd_insert_page() 2019-05-25 18:23:24 +02:00
cryptoloop.c block: cryptoloop - Fix build warning 2017-09-26 07:41:22 -06:00
DAC960.c block/DAC960.c: make some arrays static const, shrinks object size 2018-08-21 11:00:17 -06:00
DAC960.h DAC960: don't use block layer bounce buffers 2018-05-11 15:07:54 -06:00
floppy.c floppy: fix usercopy direction 2019-09-21 07:17:14 +02:00
Kconfig cdrom: Use struct scsi_sense_hdr internally 2018-08-02 15:22:39 -06:00
loop.c loop: Add LOOP_SET_DIRECT_IO to compat ioctl 2019-10-05 13:09:39 +02:00
loop.h block/loop: Use global lock for ioctl() operation. 2019-01-22 21:40:36 +01:00
Makefile block: Rename the null_blk_mod kernel module back into null_blk 2018-07-24 09:54:36 -06:00
nbd.c nbd: fix crash when the blksize is zero 2019-10-11 18:21:26 +02:00
null_blk.h null_blk: fix zoned support for non-rq based operation 2018-09-12 18:21:11 -06:00
null_blk_main.c block: null_blk: fix race condition for null_del_dev 2019-07-26 09:14:07 +02:00
null_blk_zoned.c null_blk: fix zoned support for non-rq based operation 2018-09-12 18:21:11 -06:00
pktcdvd.c pktcdvd: remove warning on attempting to register non-passthrough dev 2019-10-07 18:57:15 +02:00
ps3disk.c ps3disk: handle highmem pages 2018-05-11 15:08:03 -06:00
ps3vram.c treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
rbd.c rbd: don't return 0 on unmap if RBD_DEV_FLAG_REMOVING is set 2019-01-16 22:04:36 +01:00
rbd_types.h
skd_main.c block: skd: Use %pad printk format for dma_addr_t values 2018-07-12 15:01:28 -06:00
skd_s1120.h skd: Use __packed only when needed 2017-08-18 08:45:29 -06:00
sunvdc.c sunvdc: Do not spin in an infinite loop when vio_ldc_send() returns EAGAIN 2019-02-12 19:47:03 +01:00
swim.c swim: fix cleanup on setup error 2018-11-13 11:08:20 -08:00
swim3.c block/swim3: Fix -EBUSY error when re-opening device after unmount 2019-02-12 19:47:18 +01:00
swim_asm.S
sx8.c block: sanitize blk_get_request calling conventions 2018-05-14 08:55:12 -06:00
umem.c block: Fix a race between the cgroup code and request queue initialization 2018-02-28 12:23:35 -07:00
umem.h
virtio_blk.c virtio-blk: limit number of hw queues by nr_cpu_ids 2019-05-10 17:54:09 +02:00
xen-blkfront.c xen-blkfront: switch kcalloc to kvcalloc for large array allocation 2019-06-11 12:20:53 +02:00
xsysace.c xsysace: Fix error handling in ace_setup 2019-05-08 07:21:51 +02:00
z2ram.c treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00