From e82fc7855749aa197740a60ef22c492c41ea5d5f Mon Sep 17 00:00:00 2001
From: Ming Lei <ming.lei@redhat.com>
Date: Sat, 27 Mar 2021 15:13:09 +0800
Subject: [PATCH] block: don't create too many partitions
Commit a33df75c6328 ("block: use an xarray for disk->part_tbl") drops the
check on max supported number of partitionsr, and allows partition with
bigger partition numbers 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.
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reported-by: syzbot+8fede7e30c7cee0de139@syzkaller.appspotmail.com
Fixes: a33df75c6328 ("block: use an xarray for disk->part_tbl")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
block/partitions/core.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/block/partitions/core.c b/block/partitions/core.c
index 1a7558917c47d..46f055bc7ecb3 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.
--
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