From: Mingzhe Zou Date: Sun, 22 Mar 2026 13:41:02 +0000 (+0800) Subject: bcache: fix cached_dev.sb_bio use-after-free and crash X-Git-Tag: v6.19.14~9 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4f71c8ba2dc009042493021d94a9718fbe2ebf27;p=thirdparty%2Fkernel%2Fstable.git bcache: fix cached_dev.sb_bio use-after-free and crash commit fec114a98b8735ee89c75216c45a78e28be0f128 upstream. In our production environment, we have received multiple crash reports regarding libceph, which have caught our attention: ``` [6888366.280350] Call Trace: [6888366.280452] blk_update_request+0x14e/0x370 [6888366.280561] blk_mq_end_request+0x1a/0x130 [6888366.280671] rbd_img_handle_request+0x1a0/0x1b0 [rbd] [6888366.280792] rbd_obj_handle_request+0x32/0x40 [rbd] [6888366.280903] __complete_request+0x22/0x70 [libceph] [6888366.281032] osd_dispatch+0x15e/0xb40 [libceph] [6888366.281164] ? inet_recvmsg+0x5b/0xd0 [6888366.281272] ? ceph_tcp_recvmsg+0x6f/0xa0 [libceph] [6888366.281405] ceph_con_process_message+0x79/0x140 [libceph] [6888366.281534] ceph_con_v1_try_read+0x5d7/0xf30 [libceph] [6888366.281661] ceph_con_workfn+0x329/0x680 [libceph] ``` After analyzing the coredump file, we found that the address of dc->sb_bio has been freed. We know that cached_dev is only freed when it is stopped. Since sb_bio is a part of struct cached_dev, rather than an alloc every time. If the device is stopped while writing to the superblock, the released address will be accessed at endio. This patch hopes to wait for sb_write to complete in cached_dev_free. It should be noted that we analyzed the cause of the problem, then tell all details to the QWEN and adopted the modifications it made. Signed-off-by: Mingzhe Zou Fixes: cafe563591446 ("bcache: A block layer cache") Cc: stable@vger.kernel.org # 3.10+ Signed-off-by: Coly Li Link: https://patch.msgid.link/20260322134102.480107-1-colyli@fnnas.com Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index 238d12ffdae8..5005a26af363 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -1373,6 +1373,13 @@ static CLOSURE_CALLBACK(cached_dev_free) mutex_unlock(&bch_register_lock); + /* + * Wait for any pending sb_write to complete before free. + * The sb_bio is embedded in struct cached_dev, so we must + * ensure no I/O is in progress. + */ + closure_sync(&dc->sb_write); + if (dc->sb_disk) folio_put(virt_to_folio(dc->sb_disk));