Commit a33df75c6328 ("block: use an xarray for disk->part_tbl") drops check on max supported partitions number, and allows partition with bigger partition number to be added. However, ->bd_partno is defined as u8, so partition index of xarray table may not match with ->bd_partno. Then delete_partition() may delete one unmatched partition, and caused use-after-free. Cc: Bart Van Assche <bvanassche@xxxxxxx> Reported-by: syzbot+8fede7e30c7cee0de139@xxxxxxxxxxxxxxxxxxxxxxxxx Fixes: a33df75c6328 ("block: use an xarray for disk->part_tbl") Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> --- V2: - don't check disk_max_parts() which is supposed to not zero block/partitions/core.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/block/partitions/core.c b/block/partitions/core.c index 1a7558917c47..46f055bc7ecb 100644 --- a/block/partitions/core.c +++ b/block/partitions/core.c @@ -322,6 +322,13 @@ static struct block_device *add_partition(struct gendisk *disk, int partno, const char *dname; int err; + /* + * disk_max_parts() won't be zero, either GENHD_FL_EXT_DEVT is set + * or 'minors' is passed to alloc_disk(). + */ + if (partno >= disk_max_parts(disk)) + return ERR_PTR(-EINVAL); + /* * Partitions are not supported on zoned block devices that are used as * such. -- 2.29.2