This is a note to let you know that I've just added the patch titled
block, bfq: fix bfqq uaf in bfq_limit_depth()
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
block-bfq-fix-bfqq-uaf-in-bfq_limit_depth.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 8a745a979865f291c6bceccad4fe0f44364283eb
Author: Yu Kuai <yukuai3@xxxxxxxxxx>
Date: Fri Nov 29 17:15:09 2024 +0800
block, bfq: fix bfqq uaf in bfq_limit_depth()
[ Upstream commit e8b8344de3980709080d86c157d24e7de07d70ad ]
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@xxxxxxx>
Fixes: 76f1df88bbc2 ("bfq: Limit number of requests consumed by each cgroup")
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20241129091509.2227136-1-yukuai1@xxxxxxxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 7e0dcded5713a..dd8ca3f7ba60a 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -582,23 +582,31 @@ 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) {
@@ -643,7 +651,7 @@ 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;
}
@@ -666,7 +674,9 @@ 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;
}
@@ -704,8 +714,9 @@ 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
@@ -713,7 +724,7 @@ 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;
}
