syzbot is reporting use-after-free read at bdev_free_inode() [1], for kfree() from __alloc_disk_node() is called before bdev_free_inode() (which is called after RCU grace period) reads bdev->bd_disk and calls kfree(bdev->bd_disk). Fix use-after-free read followed by double kfree() problem by explicitly resetting bdev->bd_disk to NULL before calling iput(). Link: https://syzkaller.appspot.com/bug?extid=8281086e8a6fbfbd952a [1] Reported-by: syzbot <syzbot+8281086e8a6fbfbd952a@xxxxxxxxxxxxxxxxxxxxxxxxx> Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> --- This patch is not tested due to lack of reproducer. Is this fix correct? block/bdev.c | 1 + block/genhd.c | 1 + 2 files changed, 2 insertions(+) diff --git a/block/bdev.c b/block/bdev.c index cf2780cb44a7..f6b8bac83bd8 100644 --- a/block/bdev.c +++ b/block/bdev.c @@ -495,6 +495,7 @@ struct block_device *bdev_alloc(struct gendisk *disk, u8 partno) bdev->bd_inode = inode; bdev->bd_stats = alloc_percpu(struct disk_stats); if (!bdev->bd_stats) { + bdev->bd_disk = NULL; iput(inode); return NULL; } diff --git a/block/genhd.c b/block/genhd.c index 7b6e5e1cf956..496e8458c357 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -1268,6 +1268,7 @@ struct gendisk *__alloc_disk_node(struct request_queue *q, int node_id, out_destroy_part_tbl: xa_destroy(&disk->part_tbl); + disk->part0->bd_disk = NULL; iput(disk->part0->bd_inode); out_free_bdi: bdi_put(disk->bdi); -- 2.18.4
