On Sun, Oct 27, 2019 at 02:46:07PM +0100, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From f7daefe4231e57381d92c2e2ad905a899c28e402 Mon Sep 17 00:00:00 2001
From: Chenwandun <chenwandun@xxxxxxxxxx>
Date: Fri, 18 Oct 2019 20:20:14 -0700
Subject: [PATCH] zram: fix race between backing_dev_show and backing_dev_store
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@xxxxxxxxxx
Signed-off-by: Chenwandun <chenwandun@xxxxxxxxxx>
Acked-by: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [4.14+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
This conflict was due to the refactoring done by 7e5292831b346 ("zram:
refactor flags and writeback stuff"). I originally wanted to take it as
well, but there were too many changes in 4.14, so instead I fixed up the
original conflict and queued it up for 4.19 and 4.14.
--
Thanks,
Sasha
