>From be88e559ec13f49b1c3aec2457c14c70f6b1926a Mon Sep 17 00:00:00 2001 From: Tetsuo Handa <[email protected]> Date: Mon, 23 Apr 2018 11:21:03 +0900 Subject: [PATCH] bdi: Fix use after free bug in debugfs_remove()
syzbot is reporting use after free bug in debugfs_remove() [1]. This is because fault injection made memory allocation for debugfs_create_file() from bdi_debug_register() from bdi_register_va() fail and continued with setting WB_registered. But when debugfs_remove() is called from debugfs_remove(bdi->debug_dir) from bdi_debug_unregister() from bdi_unregister() from release_bdi() because WB_registered was set by bdi_register_va(), IS_ERR_OR_NULL(bdi->debug_dir) == false despite debugfs_remove(bdi->debug_dir) was already called from bdi_register_va(). Fix this by making IS_ERR_OR_NULL(bdi->debug_dir) == true. [1] https://syzkaller.appspot.com/bug?id=5ab4efd91a96dcea9b68104f159adf4af2a6dfc1 Signed-off-by: Tetsuo Handa <[email protected]> Reported-by: syzbot <[email protected]> Fixes: 97f07697932e6faf ("bdi: convert bdi_debug_register to int") Cc: weiping zhang <[email protected]> Cc: Jan Kara <[email protected]> Cc: Jens Axboe <[email protected]> --- mm/backing-dev.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/backing-dev.c b/mm/backing-dev.c index 023190c..7fe73fa 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -115,6 +115,7 @@ static int bdi_debug_register(struct backing_dev_info *bdi, const char *name) bdi, &bdi_debug_stats_fops); if (!bdi->debug_stats) { debugfs_remove(bdi->debug_dir); + bdi->debug_dir = NULL; return -ENOMEM; } -- 1.8.3.1
