On Sun, Oct 27, 2019 at 02:46:07PM +0100, gregkh@linuxfoundation.org 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@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From f7daefe4231e57381d92c2e2ad905a899c28e402 Mon Sep 17 00:00:00 2001 From: Chenwandun chenwandun@huawei.com 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@huawei... 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
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.