From f53823c18131e755905b4f654196fd2cc3953f6e Mon Sep 17 00:00:00 2001 From: Tetsuo Handa 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 Reported-by: syzbot Fixes: 97f07697932e6faf ("bdi: convert bdi_debug_register to int") Cc: weiping zhang Reviewed-by: Greg Kroah-Hartman Reviewed-by: Jan Kara Signed-off-by: Jens Axboe --- mm/backing-dev.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/backing-dev.c b/mm/backing-dev.c index fa5e6d7406d1..7441bd93b732 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; } -- 2.30.2