| From bippy-1.2.0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@kernel.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2021-47379: blk-cgroup: fix UAF by grabbing blkcg lock before destroying blkg pd |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| blk-cgroup: fix UAF by grabbing blkcg lock before destroying blkg pd |
| |
| KASAN reports a use-after-free report when doing fuzz test: |
| |
| [693354.104835] ================================================================== |
| [693354.105094] BUG: KASAN: use-after-free in bfq_io_set_weight_legacy+0xd3/0x160 |
| [693354.105336] Read of size 4 at addr ffff888be0a35664 by task sh/1453338 |
| |
| [693354.105607] CPU: 41 PID: 1453338 Comm: sh Kdump: loaded Not tainted 4.18.0-147 |
| [693354.105610] Hardware name: Huawei 2288H V5/BC11SPSCB0, BIOS 0.81 07/02/2018 |
| [693354.105612] Call Trace: |
| [693354.105621] dump_stack+0xf1/0x19b |
| [693354.105626] ? show_regs_print_info+0x5/0x5 |
| [693354.105634] ? printk+0x9c/0xc3 |
| [693354.105638] ? cpumask_weight+0x1f/0x1f |
| [693354.105648] print_address_description+0x70/0x360 |
| [693354.105654] kasan_report+0x1b2/0x330 |
| [693354.105659] ? bfq_io_set_weight_legacy+0xd3/0x160 |
| [693354.105665] ? bfq_io_set_weight_legacy+0xd3/0x160 |
| [693354.105670] bfq_io_set_weight_legacy+0xd3/0x160 |
| [693354.105675] ? bfq_cpd_init+0x20/0x20 |
| [693354.105683] cgroup_file_write+0x3aa/0x510 |
| [693354.105693] ? ___slab_alloc+0x507/0x540 |
| [693354.105698] ? cgroup_file_poll+0x60/0x60 |
| [693354.105702] ? 0xffffffff89600000 |
| [693354.105708] ? usercopy_abort+0x90/0x90 |
| [693354.105716] ? mutex_lock+0xef/0x180 |
| [693354.105726] kernfs_fop_write+0x1ab/0x280 |
| [693354.105732] ? cgroup_file_poll+0x60/0x60 |
| [693354.105738] vfs_write+0xe7/0x230 |
| [693354.105744] ksys_write+0xb0/0x140 |
| [693354.105749] ? __ia32_sys_read+0x50/0x50 |
| [693354.105760] do_syscall_64+0x112/0x370 |
| [693354.105766] ? syscall_return_slowpath+0x260/0x260 |
| [693354.105772] ? do_page_fault+0x9b/0x270 |
| [693354.105779] ? prepare_exit_to_usermode+0xf9/0x1a0 |
| [693354.105784] ? enter_from_user_mode+0x30/0x30 |
| [693354.105793] entry_SYSCALL_64_after_hwframe+0x65/0xca |
| |
| [693354.105875] Allocated by task 1453337: |
| [693354.106001] kasan_kmalloc+0xa0/0xd0 |
| [693354.106006] kmem_cache_alloc_node_trace+0x108/0x220 |
| [693354.106010] bfq_pd_alloc+0x96/0x120 |
| [693354.106015] blkcg_activate_policy+0x1b7/0x2b0 |
| [693354.106020] bfq_create_group_hierarchy+0x1e/0x80 |
| [693354.106026] bfq_init_queue+0x678/0x8c0 |
| [693354.106031] blk_mq_init_sched+0x1f8/0x460 |
| [693354.106037] elevator_switch_mq+0xe1/0x240 |
| [693354.106041] elevator_switch+0x25/0x40 |
| [693354.106045] elv_iosched_store+0x1a1/0x230 |
| [693354.106049] queue_attr_store+0x78/0xb0 |
| [693354.106053] kernfs_fop_write+0x1ab/0x280 |
| [693354.106056] vfs_write+0xe7/0x230 |
| [693354.106060] ksys_write+0xb0/0x140 |
| [693354.106064] do_syscall_64+0x112/0x370 |
| [693354.106069] entry_SYSCALL_64_after_hwframe+0x65/0xca |
| |
| [693354.106114] Freed by task 1453336: |
| [693354.106225] __kasan_slab_free+0x130/0x180 |
| [693354.106229] kfree+0x90/0x1b0 |
| [693354.106233] blkcg_deactivate_policy+0x12c/0x220 |
| [693354.106238] bfq_exit_queue+0xf5/0x110 |
| [693354.106241] blk_mq_exit_sched+0x104/0x130 |
| [693354.106245] __elevator_exit+0x45/0x60 |
| [693354.106249] elevator_switch_mq+0xd6/0x240 |
| [693354.106253] elevator_switch+0x25/0x40 |
| [693354.106257] elv_iosched_store+0x1a1/0x230 |
| [693354.106261] queue_attr_store+0x78/0xb0 |
| [693354.106264] kernfs_fop_write+0x1ab/0x280 |
| [693354.106268] vfs_write+0xe7/0x230 |
| [693354.106271] ksys_write+0xb0/0x140 |
| [693354.106275] do_syscall_64+0x112/0x370 |
| [693354.106280] entry_SYSCALL_64_after_hwframe+0x65/0xca |
| |
| [693354.106329] The buggy address belongs to the object at ffff888be0a35580 |
| which belongs to the cache kmalloc-1k of size 1024 |
| [693354.106736] The buggy address is located 228 bytes inside of |
| 1024-byte region [ffff888be0a35580, ffff888be0a35980) |
| [693354.107114] The buggy address belongs to the page: |
| [693354.107273] page:ffffea002f828c00 count:1 mapcount:0 mapping:ffff888107c17080 index:0x0 compound_mapcount: 0 |
| [693354.107606] flags: 0x17ffffc0008100(slab|head) |
| [693354.107760] raw: 0017ffffc0008100 ffffea002fcbc808 ffffea0030bd3a08 ffff888107c17080 |
| [693354.108020] raw: 0000000000000000 00000000001c001c 00000001ffffffff 0000000000000000 |
| [693354.108278] page dumped because: kasan: bad access detected |
| |
| [693354.108511] Memory state around the buggy address: |
| [693354.108671] ffff888be0a35500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc |
| [693354.116396] ffff888be0a35580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb |
| [693354.124473] >ffff888be0a35600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb |
| [693354.132421] ^ |
| [693354.140284] ffff888be0a35680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb |
| [693354.147912] ffff888be0a35700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb |
| [693354.155281] ================================================================== |
| |
| blkgs are protected by both queue and blkcg locks and holding |
| either should stabilize them. However, the path of destroying |
| blkg policy data is only protected by queue lock in |
| blkcg_activate_policy()/blkcg_deactivate_policy(). Other tasks |
| can get the blkg policy data before the blkg policy data is |
| destroyed, and use it after destroyed, which will result in a |
| use-after-free. |
| |
| CPU0 CPU1 |
| blkcg_deactivate_policy |
| spin_lock_irq(&q->queue_lock) |
| bfq_io_set_weight_legacy |
| spin_lock_irq(&blkcg->lock) |
| blkg_to_bfqg(blkg) |
| pd_to_bfqg(blkg->pd[pol->plid]) |
| ^^^^^^blkg->pd[pol->plid] != NULL |
| bfqg != NULL |
| pol->pd_free_fn(blkg->pd[pol->plid]) |
| pd_to_bfqg(blkg->pd[pol->plid]) |
| bfqg_put(bfqg) |
| kfree(bfqg) |
| blkg->pd[pol->plid] = NULL |
| spin_unlock_irq(q->queue_lock); |
| bfq_group_set_weight(bfqg, val, 0) |
| bfqg->entity.new_weight |
| ^^^^^^trigger uaf here |
| spin_unlock_irq(&blkcg->lock); |
| |
| Fix by grabbing the matching blkcg lock before trying to |
| destroy blkg policy data. |
| |
| The Linux kernel CVE team has assigned CVE-2021-47379 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 4.17 with commit 946b81da114b8ba5c74bb01e57c0c6eca2bdc801 and fixed in 5.4.150 with commit d12ddd843f1877de1f7dd2aeea4907cf9ff3ac08 |
| Issue introduced in 4.17 with commit 946b81da114b8ba5c74bb01e57c0c6eca2bdc801 and fixed in 5.10.70 with commit f58d305887ad7b24986d58e881f6806bb81b2bdf |
| Issue introduced in 4.17 with commit 946b81da114b8ba5c74bb01e57c0c6eca2bdc801 and fixed in 5.14.9 with commit 7c2c69e010431b0157c9454adcdd2305809bf9fb |
| Issue introduced in 4.17 with commit 946b81da114b8ba5c74bb01e57c0c6eca2bdc801 and fixed in 5.15 with commit 858560b27645e7e97aca37ee8f232cccd658fbd2 |
| Issue introduced in 4.14.51 with commit 9d5e2d69705fed4ab527f5a283b90ae602f4e0fd |
| Issue introduced in 4.16.17 with commit 3ca6e949b751fa3dfbf475ce635364cef543738b |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2021-47379 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| block/blk-cgroup.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/d12ddd843f1877de1f7dd2aeea4907cf9ff3ac08 |
| https://git.kernel.org/stable/c/f58d305887ad7b24986d58e881f6806bb81b2bdf |
| https://git.kernel.org/stable/c/7c2c69e010431b0157c9454adcdd2305809bf9fb |
| https://git.kernel.org/stable/c/858560b27645e7e97aca37ee8f232cccd658fbd2 |
