High · published December 24, 2025
In the Linux kernel, the following vulnerability has been resolved:
md/raid5: Remove unnecessary bio_put() in raid5_read_one_chunk()
When running chunk-sized reads on disks with badblocks duplicate bio
free/puts are observed:
=============================================================================
BUG bio-200 (Not tainted): Object already free
-----------------------------------------------------------------------------
Allocated in mempool_alloc_slab+0x17/0x20 age=3 cpu=2 pid=7504
__slab_alloc.constprop.0+0x5a/0xb0
kmem_cache_alloc+0x31e/0x330
mempool_alloc_slab+0x17/0x20
mempool_alloc+0x100/0x2b0
bio_alloc_bioset+0x181/0x460
do_mpage_readpage+0x776/0xd00
mpage_readahead+0x166/0x320
blkdev_readahead+0x15/0x20
read_pages+0x13f/0x5f0
page_cache_ra_unbounded+0x18d/0x220
force_page_cache_ra+0x181/0x1c0
page_cache_sync_ra+0x65/0xb0
filemap_get_pages+0x1df/0xaf0
filemap_read+0x1e1/0x700
blkdev_read_iter+0x1e5/0x330
vfs_read+0x42a/0x570
Freed in mempool_free_slab+0x17/0x20 age=3 cpu=2 pid=7504
kmem_cache_free+0x46d/0x490
mempool_free_slab+0x17/0x20
mempool_free+0x66/0x190
bio_free+0x78/0x90
bio_put+0x100/0x1a0
raid5_make_request+0x2259/0x2450
md_handle_request+0x402/0x600
md_submit_bio+0xd9/0x120
__submit_bio+0x11f/0x1b0
submit_bio_noacct_nocheck+0x204/0x480
submit_bio_noacct+0x32e/0xc70
submit_bio+0x98/0x1a0
mpage_readahead+0x250/0x320
blkdev_readahead+0x15/0x20
read_pages+0x13f/0x5f0
page_cache_ra_unbounded+0x18d/0x220
Slab 0xffffea000481b600 objects=21 used=0 fp=0xffff8881206d8940 flags=0x17ffffc0010201(locked|slab|head|node=0|zone=2|lastcpupid=0x1fffff)
CPU: 0 PID: 34525 Comm: kworker/u24:2 Not tainted 6.0.0-rc2-localyes-265166-gf11c5343fa3f #143
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-1ubuntu1.1 04/01/2014
Workqueue: raid5wq raid5_do_work
Call Trace:
<TASK>
dump_stack_lvl+0x5a/0x78
dump_stack+0x10/0x16
print_trailer+0x158/0x165
object_err+0x35/0x50
free_debug_processing.cold+0xb7/0xbe
__slab_free+0x1ae/0x330
kmem_cache_free+0x46d/0x490
mempool_free_slab+0x17/0x20
mempool_free+0x66/0x190
bio_free+0x78/0x90
bio_put+0x100/0x1a0
mpage_end_io+0x36/0x150
bio_endio+0x2fd/0x360
md_end_io_acct+0x7e/0x90
bio_endio+0x2fd/0x360
handle_failed_stripe+0x960/0xb80
handle_stripe+0x1348/0x3760
handle_active_stripes.constprop.0+0x72a/0xaf0
raid5_do_work+0x177/0x330
process_one_work+0x616/0xb20
worker_thread+0x2bd/0x6f0
kthread+0x179/0x1b0
ret_from_fork+0x22/0x30
</TASK>
The double free is caused by an unnecessary bio_put() in the
if(is_badblock(...)) error path in raid5_read_one_chunk().
The error path was moved ahead of bio_alloc_clone() in c82aa1b76787c
("md/raid5: move checking badblock before clone bio in
raid5_read_one_chunk"). The previous code checked and freed align_bio
which required a bio_put. After the move that is no longer needed as
raid_bio is returned to the control of the common io path which
performs its own endio resulting in a double free on bad device blocks.