From: Yu Kuai yukuai3@huawei.com
commit e8b8344de3980709080d86c157d24e7de07d70ad upstream.
Set new allocated bfqq to bic or remove freed bfqq from bic are both protected by bfqd->lock, however bfq_limit_depth() is deferencing bfqq from bic without the lock, this can lead to UAF if the io_context is shared by multiple tasks.
For example, test bfq with io_uring can trigger following UAF in v6.6:
================================================================== BUG: KASAN: slab-use-after-free in bfqq_group+0x15/0x50
Call Trace: <TASK> dump_stack_lvl+0x47/0x80 print_address_description.constprop.0+0x66/0x300 print_report+0x3e/0x70 kasan_report+0xb4/0xf0 bfqq_group+0x15/0x50 bfqq_request_over_limit+0x130/0x9a0 bfq_limit_depth+0x1b5/0x480 __blk_mq_alloc_requests+0x2b5/0xa00 blk_mq_get_new_requests+0x11d/0x1d0 blk_mq_submit_bio+0x286/0xb00 submit_bio_noacct_nocheck+0x331/0x400 __block_write_full_folio+0x3d0/0x640 writepage_cb+0x3b/0xc0 write_cache_pages+0x254/0x6c0 write_cache_pages+0x254/0x6c0 do_writepages+0x192/0x310 filemap_fdatawrite_wbc+0x95/0xc0 __filemap_fdatawrite_range+0x99/0xd0 filemap_write_and_wait_range.part.0+0x4d/0xa0 blkdev_read_iter+0xef/0x1e0 io_read+0x1b6/0x8a0 io_issue_sqe+0x87/0x300 io_wq_submit_work+0xeb/0x390 io_worker_handle_work+0x24d/0x550 io_wq_worker+0x27f/0x6c0 ret_from_fork_asm+0x1b/0x30 </TASK>
Allocated by task 808602: kasan_save_stack+0x1e/0x40 kasan_set_track+0x21/0x30 __kasan_slab_alloc+0x83/0x90 kmem_cache_alloc_node+0x1b1/0x6d0 bfq_get_queue+0x138/0xfa0 bfq_get_bfqq_handle_split+0xe3/0x2c0 bfq_init_rq+0x196/0xbb0 bfq_insert_request.isra.0+0xb5/0x480 bfq_insert_requests+0x156/0x180 blk_mq_insert_request+0x15d/0x440 blk_mq_submit_bio+0x8a4/0xb00 submit_bio_noacct_nocheck+0x331/0x400 __blkdev_direct_IO_async+0x2dd/0x330 blkdev_write_iter+0x39a/0x450 io_write+0x22a/0x840 io_issue_sqe+0x87/0x300 io_wq_submit_work+0xeb/0x390 io_worker_handle_work+0x24d/0x550 io_wq_worker+0x27f/0x6c0 ret_from_fork+0x2d/0x50 ret_from_fork_asm+0x1b/0x30
Freed by task 808589: kasan_save_stack+0x1e/0x40 kasan_set_track+0x21/0x30 kasan_save_free_info+0x27/0x40 __kasan_slab_free+0x126/0x1b0 kmem_cache_free+0x10c/0x750 bfq_put_queue+0x2dd/0x770 __bfq_insert_request.isra.0+0x155/0x7a0 bfq_insert_request.isra.0+0x122/0x480 bfq_insert_requests+0x156/0x180 blk_mq_dispatch_plug_list+0x528/0x7e0 blk_mq_flush_plug_list.part.0+0xe5/0x590 __blk_flush_plug+0x3b/0x90 blk_finish_plug+0x40/0x60 do_writepages+0x19d/0x310 filemap_fdatawrite_wbc+0x95/0xc0 __filemap_fdatawrite_range+0x99/0xd0 filemap_write_and_wait_range.part.0+0x4d/0xa0 blkdev_read_iter+0xef/0x1e0 io_read+0x1b6/0x8a0 io_issue_sqe+0x87/0x300 io_wq_submit_work+0xeb/0x390 io_worker_handle_work+0x24d/0x550 io_wq_worker+0x27f/0x6c0 ret_from_fork+0x2d/0x50 ret_from_fork_asm+0x1b/0x30
Fix the problem by protecting bic_to_bfqq() with bfqd->lock.
CC: Jan Kara jack@suse.cz Fixes: 76f1df88bbc2 ("bfq: Limit number of requests consumed by each cgroup") Signed-off-by: Yu Kuai yukuai3@huawei.com Link: https://lore.kernel.org/r/20241129091509.2227136-1-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Hagar Hemdan hagarhem@amazon.com --- block/bfq-iosched.c | 37 ++++++++++++++++++++++++------------- 1 file changed, 24 insertions(+), 13 deletions(-)
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 76b2e66d09070..d1c62a4e8c357 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -581,23 +581,31 @@ static struct request *bfq_choose_req(struct bfq_data *bfqd, #define BFQ_LIMIT_INLINE_DEPTH 16
#ifdef CONFIG_BFQ_GROUP_IOSCHED -static bool bfqq_request_over_limit(struct bfq_queue *bfqq, int limit) +static bool bfqq_request_over_limit(struct bfq_data *bfqd, + struct bfq_io_cq *bic, blk_opf_t opf, + unsigned int act_idx, int limit) { - struct bfq_data *bfqd = bfqq->bfqd; - struct bfq_entity *entity = &bfqq->entity; struct bfq_entity *inline_entities[BFQ_LIMIT_INLINE_DEPTH]; struct bfq_entity **entities = inline_entities; - int depth, level, alloc_depth = BFQ_LIMIT_INLINE_DEPTH; - int class_idx = bfqq->ioprio_class - 1; + int alloc_depth = BFQ_LIMIT_INLINE_DEPTH; struct bfq_sched_data *sched_data; + struct bfq_entity *entity; + struct bfq_queue *bfqq; unsigned long wsum; bool ret = false; - - if (!entity->on_st_or_in_serv) - return false; + int depth; + int level;
retry: spin_lock_irq(&bfqd->lock); + bfqq = bic_to_bfqq(bic, op_is_sync(opf), act_idx); + if (!bfqq) + goto out; + + entity = &bfqq->entity; + if (!entity->on_st_or_in_serv) + goto out; + /* +1 for bfqq entity, root cgroup not included */ depth = bfqg_to_blkg(bfqq_group(bfqq))->blkcg->css.cgroup->level + 1; if (depth > alloc_depth) { @@ -642,7 +650,7 @@ static bool bfqq_request_over_limit(struct bfq_queue *bfqq, int limit) * class. */ wsum = 0; - for (i = 0; i <= class_idx; i++) { + for (i = 0; i <= bfqq->ioprio_class - 1; i++) { wsum = wsum * IOPRIO_BE_NR + sched_data->service_tree[i].wsum; } @@ -665,7 +673,9 @@ static bool bfqq_request_over_limit(struct bfq_queue *bfqq, int limit) return ret; } #else -static bool bfqq_request_over_limit(struct bfq_queue *bfqq, int limit) +static bool bfqq_request_over_limit(struct bfq_data *bfqd, + struct bfq_io_cq *bic, blk_opf_t opf, + unsigned int act_idx, int limit) { return false; } @@ -703,8 +713,9 @@ static void bfq_limit_depth(blk_opf_t opf, struct blk_mq_alloc_data *data) }
for (act_idx = 0; bic && act_idx < bfqd->num_actuators; act_idx++) { - struct bfq_queue *bfqq = - bic_to_bfqq(bic, op_is_sync(opf), act_idx); + /* Fast path to check if bfqq is already allocated. */ + if (!bic_to_bfqq(bic, op_is_sync(opf), act_idx)) + continue;
/* * Does queue (or any parent entity) exceed number of @@ -712,7 +723,7 @@ static void bfq_limit_depth(blk_opf_t opf, struct blk_mq_alloc_data *data) * limit depth so that it cannot consume more * available requests and thus starve other entities. */ - if (bfqq && bfqq_request_over_limit(bfqq, limit)) { + if (bfqq_request_over_limit(bfqd, bic, opf, act_idx, limit)) { depth = 1; break; }