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Message-Id: <20191104212126.523252383@linuxfoundation.org>
Date: Mon, 4 Nov 2019 22:43:14 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Chenwandun <chenwandun@...wei.com>,
Minchan Kim <minchan@...nel.org>,
Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
Jens Axboe <axboe@...nel.dk>,
Andrew Morton <akpm@...ux-foundation.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 001/149] 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@...wei.com>
Acked-by: Minchan Kim <minchan@...nel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc: Jens Axboe <axboe@...nel.dk>
Cc: <stable@...r.kernel.org> [4.14+]
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
drivers/block/zram/zram_drv.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 70cbd0ee1b076..76abe40bfa83b 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;
--
2.20.1
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