[PATCH] btrfs: zoned: fix double free of bitmaps on clone failure

[PATCH] btrfs: zoned: fix double free of bitmaps on clone failure

[Thomas Fourier]

btrfs_clone_dev_zone_info() duplicates the original orig_dev->zone_info
with kmemdup(), which also copies the seq_zones, empty_zones and
active_zones pointers. The clone then replaces them one by one with
fresh bitmaps. If one of the allocations fails, the error path frees all
three pointers, including those not yet replaced, which still point to
the bitmaps owned by the original device.

Clear the three pointers right after kmemdup() so the error path only frees
what this function allocated.

Fixes: 21e61ec6d0bb ("btrfs: zoned: clone zoned device info when cloning a device")
Signed-off-by: Thomas Fourier <fourier.thomas@gmail.com>
---
 fs/btrfs/zoned.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
index 08a15465a087..7dab7aac7b96 100644
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -645,6 +645,11 @@ struct btrfs_zoned_device_info *btrfs_clone_dev_zone_info(struct btrfs_device *o
 	if (!zone_info)
 		return NULL;
 
+	/* Don't let the error path free the bitmaps still owned by @orig_dev. */
+	zone_info->seq_zones = NULL;
+	zone_info->empty_zones = NULL;
+	zone_info->active_zones = NULL;
+
 	zone_info->seq_zones = bitmap_zalloc(zone_info->nr_zones, GFP_KERNEL);
 	if (!zone_info->seq_zones)
 		goto out;
-- 
2.53.0

Re: [PATCH] btrfs: zoned: fix double free of bitmaps on clone failure

[Johannes Thumshirn]

Looks good,

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>