CVE: CVE-2022-50752
Published: 2025-12-24
Description: 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.
References: https://git.kernel.org/stable/c/21a9c7354aa59e97e26ece5f0a609c8bfa43020d; https://git.kernel.org/stable/c/7a37c58ee72e1fadd22c4ee990cb74c2ca2280e7; https://git.kernel.org/stable/c/c0fd5d4d8fd7b1a50306d7a23c720cf808f41fdf