From: Yu Kuai yukuai3@huawei.com

[ Upstream commit 3802f73bd80766d70f319658f334754164075bc3 ]

blk_mq_clear_flush_rq_mapping() is not called during scsi probe, by checking blk_queue_init_done(). However, QUEUE_FLAG_INIT_DONE is cleared in del_gendisk by commit aec89dc5d421 ("block: keep q_usage_counter in atomic mode after del_gendisk"), hence for disk like scsi, following blk_mq_destroy_queue() will not clear flush rq from tags->rqs[] as well, cause following uaf that is found by our syzkaller for v6.6:

================================================================== BUG: KASAN: slab-use-after-free in blk_mq_find_and_get_req+0x16e/0x1a0 block/blk-mq-tag.c:261 Read of size 4 at addr ffff88811c969c20 by task kworker/1:2H/224909

CPU: 1 PID: 224909 Comm: kworker/1:2H Not tainted 6.6.0-ga836a5060850 #32 Workqueue: kblockd blk_mq_timeout_work Call Trace:

__dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x91/0xf0 lib/dump_stack.c:106 print_address_description.constprop.0+0x66/0x300 mm/kasan/report.c:364 print_report+0x3e/0x70 mm/kasan/report.c:475 kasan_report+0xb8/0xf0 mm/kasan/report.c:588 blk_mq_find_and_get_req+0x16e/0x1a0 block/blk-mq-tag.c:261 bt_iter block/blk-mq-tag.c:288 [inline] __sbitmap_for_each_set include/linux/sbitmap.h:295 [inline] sbitmap_for_each_set include/linux/sbitmap.h:316 [inline] bt_for_each+0x455/0x790 block/blk-mq-tag.c:325 blk_mq_queue_tag_busy_iter+0x320/0x740 block/blk-mq-tag.c:534 blk_mq_timeout_work+0x1a3/0x7b0 block/blk-mq.c:1673 process_one_work+0x7c4/0x1450 kernel/workqueue.c:2631 process_scheduled_works kernel/workqueue.c:2704 [inline] worker_thread+0x804/0xe40 kernel/workqueue.c:2785 kthread+0x346/0x450 kernel/kthread.c:388 ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:293

Allocated by task 942: kasan_save_stack+0x22/0x50 mm/kasan/common.c:45 kasan_set_track+0x25/0x30 mm/kasan/common.c:52 ____kasan_kmalloc mm/kasan/common.c:374 [inline] __kasan_kmalloc mm/kasan/common.c:383 [inline] __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:380 kasan_kmalloc include/linux/kasan.h:198 [inline] __do_kmalloc_node mm/slab_common.c:1007 [inline] __kmalloc_node+0x69/0x170 mm/slab_common.c:1014 kmalloc_node include/linux/slab.h:620 [inline] kzalloc_node include/linux/slab.h:732 [inline] blk_alloc_flush_queue+0x144/0x2f0 block/blk-flush.c:499 blk_mq_alloc_hctx+0x601/0x940 block/blk-mq.c:3788 blk_mq_alloc_and_init_hctx+0x27f/0x330 block/blk-mq.c:4261 blk_mq_realloc_hw_ctxs+0x488/0x5e0 block/blk-mq.c:4294 blk_mq_init_allocated_queue+0x188/0x860 block/blk-mq.c:4350 blk_mq_init_queue_data block/blk-mq.c:4166 [inline] blk_mq_init_queue+0x8d/0x100 block/blk-mq.c:4176 scsi_alloc_sdev+0x843/0xd50 drivers/scsi/scsi_scan.c:335 scsi_probe_and_add_lun+0x77c/0xde0 drivers/scsi/scsi_scan.c:1189 __scsi_scan_target+0x1fc/0x5a0 drivers/scsi/scsi_scan.c:1727 scsi_scan_channel drivers/scsi/scsi_scan.c:1815 [inline] scsi_scan_channel+0x14b/0x1e0 drivers/scsi/scsi_scan.c:1791 scsi_scan_host_selected+0x2fe/0x400 drivers/scsi/scsi_scan.c:1844 scsi_scan+0x3a0/0x3f0 drivers/scsi/scsi_sysfs.c:151 store_scan+0x2a/0x60 drivers/scsi/scsi_sysfs.c:191 dev_attr_store+0x5c/0x90 drivers/base/core.c:2388 sysfs_kf_write+0x11c/0x170 fs/sysfs/file.c:136 kernfs_fop_write_iter+0x3fc/0x610 fs/kernfs/file.c:338 call_write_iter include/linux/fs.h:2083 [inline] new_sync_write+0x1b4/0x2d0 fs/read_write.c:493 vfs_write+0x76c/0xb00 fs/read_write.c:586 ksys_write+0x127/0x250 fs/read_write.c:639 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_64+0x70/0x120 arch/x86/entry/common.c:81 entry_SYSCALL_64_after_hwframe+0x78/0xe2

Freed by task 244687: kasan_save_stack+0x22/0x50 mm/kasan/common.c:45 kasan_set_track+0x25/0x30 mm/kasan/common.c:52 kasan_save_free_info+0x2b/0x50 mm/kasan/generic.c:522 ____kasan_slab_free mm/kasan/common.c:236 [inline] __kasan_slab_free+0x12a/0x1b0 mm/kasan/common.c:244 kasan_slab_free include/linux/kasan.h:164 [inline] slab_free_hook mm/slub.c:1815 [inline] slab_free_freelist_hook mm/slub.c:1841 [inline] slab_free mm/slub.c:3807 [inline] __kmem_cache_free+0xe4/0x520 mm/slub.c:3820 blk_free_flush_queue+0x40/0x60 block/blk-flush.c:520 blk_mq_hw_sysfs_release+0x4a/0x170 block/blk-mq-sysfs.c:37 kobject_cleanup+0x136/0x410 lib/kobject.c:689 kobject_release lib/kobject.c:720 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x119/0x140 lib/kobject.c:737 blk_mq_release+0x24f/0x3f0 block/blk-mq.c:4144 blk_free_queue block/blk-core.c:298 [inline] blk_put_queue+0xe2/0x180 block/blk-core.c:314 blkg_free_workfn+0x376/0x6e0 block/blk-cgroup.c:144 process_one_work+0x7c4/0x1450 kernel/workqueue.c:2631 process_scheduled_works kernel/workqueue.c:2704 [inline] worker_thread+0x804/0xe40 kernel/workqueue.c:2785 kthread+0x346/0x450 kernel/kthread.c:388 ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:293

Other than blk_mq_clear_flush_rq_mapping(), the flag is only used in blk_register_queue() from initialization path, hence it's safe not to clear the flag in del_gendisk. And since QUEUE_FLAG_REGISTERED already make sure that queue should only be registered once, there is no need to test the flag as well.

Fixes: 6cfeadbff3f8 ("blk-mq: don't clear flush_rq from tags->rqs[]") Depends-on: commit aec89dc5d421 ("block: keep q_usage_counter in atomic mode after del_gendisk") Signed-off-by: Yu Kuai yukuai3@huawei.com Reviewed-by: Ming Lei ming.lei@redhat.com Link: https://lore.kernel.org/r/20241104110005.1412161-1-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: BRUNO VERNAY bruno.vernay@se.com Signed-off-by: Hugo SIMELIERE hsimeliere.opensource@witekio.com --- block/blk-sysfs.c | 6 ++---- block/genhd.c | 9 +++------ 2 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index a82bdec923b2..c74e8273511a 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -858,10 +858,8 @@ int blk_register_queue(struct gendisk *disk) * faster to shut down and is made fully functional here as * request_queues for non-existent devices never get registered. */ - if (!blk_queue_init_done(q)) { - blk_queue_flag_set(QUEUE_FLAG_INIT_DONE, q); - percpu_ref_switch_to_percpu(&q->q_usage_counter); - } + blk_queue_flag_set(QUEUE_FLAG_INIT_DONE, q); + percpu_ref_switch_to_percpu(&q->q_usage_counter);

return ret;

diff --git a/block/genhd.c b/block/genhd.c index 146ce13b192b..8256e11f85b7 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -685,13 +685,10 @@ void del_gendisk(struct gendisk *disk) * If the disk does not own the queue, allow using passthrough requests * again. Else leave the queue frozen to fail all I/O. */ - if (!test_bit(GD_OWNS_QUEUE, &disk->state)) { - blk_queue_flag_clear(QUEUE_FLAG_INIT_DONE, q); + if (!test_bit(GD_OWNS_QUEUE, &disk->state)) __blk_mq_unfreeze_queue(q, true); - } else { - if (queue_is_mq(q)) - blk_mq_exit_queue(q); - } + else if (queue_is_mq(q)) + blk_mq_exit_queue(q); } EXPORT_SYMBOL(del_gendisk);