On Mon, Oct 14, 2019 at 05:53:59PM +0800, Chen Wandun wrote: > From: Chenwandun <chenwandun@xxxxxxxxxx> > > 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); > > get the value of zram->backing_dev too early in backing_dev_show, > that will result the value may be NULL at the begining, and not > NULL later. > > backtrace: > [<ffffff8570e0f3ec>] d_path+0xcc/0x174 > [<ffffff8570decd90>] file_path+0x10/0x18 > [<ffffff85712f7630>] backing_dev_show+0x40/0xb4 > [<ffffff85712c776c>] dev_attr_show+0x20/0x54 > [<ffffff8570e835e4>] sysfs_kf_seq_show+0x9c/0x10c > [<ffffff8570e82b98>] kernfs_seq_show+0x28/0x30 > [<ffffff8570e1c580>] seq_read+0x184/0x488 > [<ffffff8570e81ec4>] kernfs_fop_read+0x5c/0x1a4 > [<ffffff8570dee0fc>] __vfs_read+0x44/0x128 > [<ffffff8570dee310>] vfs_read+0xa0/0x138 > [<ffffff8570dee860>] SyS_read+0x54/0xb4 > > Signed-off-by: Chenwandun <chenwandun@xxxxxxxxxx> It should be stable material. Cc: <stable@xxxxxxxxxxxxxxx> [4.14+] Acked-by: Minchan Kim <minchan@xxxxxxxxxx> Thanks!
