CVE-2024-47706 Information

Nov 01, 2024 cve

Description

In the Linux kernel the following vulnerability has been resolved:

block bfq: fix possible UAF for bfqq->bic with merge chain

initial state three tasks:

 Process 1       Process 2	Process 3
  (BIC1)          (BIC2)		 (BIC3)
   |  ?            |  ?		  |  ?
   |  |            |  |		  |  |
   V  |            V  |		  V  |
   bfqq1           bfqq2		  bfqq3

process ref: 1 1 1

bfqq1 merged to bfqq2:

 Process 1       Process 2	Process 3
  (BIC1)          (BIC2)		 (BIC3)
   |               |		  |  ?
   \--------------\|		  |  |
                   V		  V  |
   bfqq1--------->bfqq2		  bfqq3

process ref: 0 2 1

bfqq2 merged to bfqq3:
```
 Process 1       Process 2	Process 3
  (BIC1)          (BIC2)		 (BIC3)
```
here -> ? | | -————-\ -————| V V bfqq1———>bfqq2———->bfqq3 process ref: 0 1 3

In this case IO from Process 1 will get bfqq2 from BIC1 first and then get bfqq3 through merge chain and finially handle IO by bfqq3. Howerver current code will think bfqq2 is owned by BIC1 like initial state and set bfqq2->bic to BIC1.

bfq_insert_request -> by Process 1 bfqq = bfq_init_rq(rq) bfqq = bfq_get_bfqq_handle_split bfqq = bic_to_bfqq -> get bfqq2 from BIC1 bfqq->ref++ rq->elv.priv[0] = bic rq->elv.priv[1] = bfqq if (bfqq_process_refs(bfqq) == 1) bfqq->bic = bic -> record BIC1 to bfqq2

__bfq_insert_request new_bfqq = bfq_setup_cooperator -> get bfqq3 from bfqq2->new_bfqq bfqq_request_freed(bfqq) new_bfqq->ref++ rq->elv.priv[1] = new_bfqq -> handle IO by bfqq3

Fix the problem by checking bfqq is from merge chain fist. And this might fix a following problem reported by our syzkaller(unreproducible):

================================================================== BUG: KASAN: slab-use-after-free in bfq_do_early_stable_merge block/bfq-iosched.c:5692 [inline] BUG: KASAN: slab-use-after-free in bfq_do_or_sched_stable_merge block/bfq-iosched.c:5805 [inline] BUG: KASAN: slab-use-after-free in bfq_get_queue+0x25b0/0x2610 block/bfq-iosched.c:5889 Write of size 1 at addr ffff888123839eb8 by task kworker/0:1H/18595

CPU: 0 PID: 18595 Comm: kworker/0:1H Tainted: G L 6.6.0-07439-gba2303cacfda 6 Hardware name: QEMU Standard PC (i440FX + PIIX 1996) BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 Workqueue: kblockd blk_mq_requeue_work Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x91/0xf0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:364 [inline] print_report+0x10d/0x610 mm/kasan/report.c:475 kasan_report+0x8e/0xc0 mm/kasan/report.c:588 bfq_do_early_stable_merge block/bfq-iosched.c:5692 [inline] bfq_do_or_sched_stable_merge block/bfq-iosched.c:5805 [inline] bfq_get_queue+0x25b0/0x2610 block/bfq-iosched.c:5889 bfq_get_bfqq_handle_split+0x169/0x5d0 block/bfq-iosched.c:6757 bfq_init_rq block/bfq-iosched.c:6876 [inline] bfq_insert_request block/bfq-iosched.c:6254 [inline] bfq_insert_requests+0x1112/0x5cf0 block/bfq-iosched.c:6304 blk_mq_insert_request+0x290/0x8d0 block/blk-mq.c:2593 blk_mq_requeue_work+0x6bc/0xa70 block/blk-mq.c:1502 process_one_work kernel/workqueue.c:2627 [inline] process_scheduled_works+0x432/0x13f0 kernel/workqueue.c:2700 worker_thread+0x6f2/0x1160 kernel/workqueue.c:2781 kthread+0x33c/0x440 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:305

Allocated by task 20776: kasan_save_stack+0x20/0x40 mm/kasan/common.c:45 kasan_set_track+0x25/0x30 mm/kasan/common.c:52 __kasan_slab_alloc+0x87/0x90 mm/kasan/common.c:328 kasan_slab_alloc include/linux/kasan.h:188 [inline] slab_post_alloc_hook mm/slab.h:763 [inline] slab_alloc_node mm/slub.c:3458 [inline] kmem_cache_alloc_node+0x1a4/0x6f0 mm/slub.c:3503 ioc_create_icq block/blk-ioc.c:370 [inline]

truncated—

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Reference

https://git.kernel.org/stable/c/e1277ae780cca4e69ef5468d4582dfd48f0b8320 https://git.kernel.org/stable/c/8aa9de02a4be2e7006e636816ce19b0d667ceaa3 https://git.kernel.org/stable/c/ddbdaad123254fb53e32480cb74a486a6868b1e0 https://git.kernel.org/stable/c/7faed2896d78e48ec96229e73b30b0af6c00a9aa https://git.kernel.org/stable/c/880692ee233ba63808182705b3333403413b58f5 https://git.kernel.org/stable/c/6d130db286ad0ea392c96ebb2551acf0d7308048 https://git.kernel.org/stable/c/18ad4df091dd5d067d2faa8fce1180b79f7041a7

Attack Complexity

LOW

Privileges Required

LOW

User Interaction Required

LOW

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

NONE

Availability Impact

NONE

Base Score

HIGH

Base Severity

5.5

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