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| author | Sasha Levin <sashal@kernel.org> | 2019-10-28 11:59:17 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-11-06 15:05:10 +0300 |
| commit | 0ca37291020ef45454d9b106bee53eb8c7e8d967 (patch) | |
| tree | edd7ae68a3b35fc827a88e6ae848e9c7732ff87d | |
| parent | ef244c3088856cf048c77231653b4c92a7b2213c (diff) | |
| download | linux-0ca37291020ef45454d9b106bee53eb8c7e8d967.tar.xz | |
zram: fix race between backing_dev_show and backing_dev_store
[ Upstream commit f7daefe4231e57381d92c2e2ad905a899c28e402 ]
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>
| -rw-r--r-- | drivers/block/zram/zram_drv.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 70cbd0ee1b07..76abe40bfa83 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -312,13 +312,14 @@ static void reset_bdev(struct zram *zram) static ssize_t backing_dev_show(struct device *dev, struct device_attribute *attr, char *buf) { + struct file *file; struct zram *zram = dev_to_zram(dev); - struct file *file = zram->backing_dev; char *p; ssize_t ret; down_read(&zram->init_lock); - if (!zram_wb_enabled(zram)) { + file = zram->backing_dev; + if (!file) { memcpy(buf, "none\n", 5); up_read(&zram->init_lock); return 5; |