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authorTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>2018-04-23 11:21:03 +0900
committerJens Axboe <axboe@kernel.dk>2018-05-03 09:36:24 -0600
commitf53823c18131e755905b4f654196fd2cc3953f6e (patch)
tree94a1ced15776f1ec274d53b337f5640201b32265 /mm/backing-dev.c
parentbdi: wake up concurrent wb_shutdown() callers. (diff)
downloadlinux-dev-f53823c18131e755905b4f654196fd2cc3953f6e.tar.xz
linux-dev-f53823c18131e755905b4f654196fd2cc3953f6e.zip
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 <penguin-kernel@I-love.SAKURA.ne.jp> Reported-by: syzbot <syzbot+049cb4ae097049dac137@syzkaller.appspotmail.com> Fixes: 97f07697932e6faf ("bdi: convert bdi_debug_register to int") Cc: weiping zhang <zhangweiping@didichuxing.com> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to '')
-rw-r--r--mm/backing-dev.c1
1 files changed, 1 insertions, 0 deletions
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;
}