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Yang Yingliang b42b0bddcb workqueue: fix UAF in pwq_unbound_release_workfn() 
I got a UAF report when doing fuzz test:

[  152.880091][ T8030] ==================================================================
[  152.881240][ T8030] BUG: KASAN: use-after-free in pwq_unbound_release_workfn+0x50/0x190
[  152.882442][ T8030] Read of size 4 at addr ffff88810d31bd00 by task kworker/3:2/8030
[  152.883578][ T8030]
[  152.883932][ T8030] CPU: 3 PID: 8030 Comm: kworker/3:2 Not tainted 5.13.0+ #249
[  152.885014][ T8030] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
[  152.886442][ T8030] Workqueue: events pwq_unbound_release_workfn
[  152.887358][ T8030] Call Trace:
[  152.887837][ T8030]  dump_stack_lvl+0x75/0x9b
[  152.888525][ T8030]  ? pwq_unbound_release_workfn+0x50/0x190
[  152.889371][ T8030]  print_address_description.constprop.10+0x48/0x70
[  152.890326][ T8030]  ? pwq_unbound_release_workfn+0x50/0x190
[  152.891163][ T8030]  ? pwq_unbound_release_workfn+0x50/0x190
[  152.891999][ T8030]  kasan_report.cold.15+0x82/0xdb
[  152.892740][ T8030]  ? pwq_unbound_release_workfn+0x50/0x190
[  152.893594][ T8030]  __asan_load4+0x69/0x90
[  152.894243][ T8030]  pwq_unbound_release_workfn+0x50/0x190
[  152.895057][ T8030]  process_one_work+0x47b/0x890
[  152.895778][ T8030]  worker_thread+0x5c/0x790
[  152.896439][ T8030]  ? process_one_work+0x890/0x890
[  152.897163][ T8030]  kthread+0x223/0x250
[  152.897747][ T8030]  ? set_kthread_struct+0xb0/0xb0
[  152.898471][ T8030]  ret_from_fork+0x1f/0x30
[  152.899114][ T8030]
[  152.899446][ T8030] Allocated by task 8884:
[  152.900084][ T8030]  kasan_save_stack+0x21/0x50
[  152.900769][ T8030]  __kasan_kmalloc+0x88/0xb0
[  152.901416][ T8030]  __kmalloc+0x29c/0x460
[  152.902014][ T8030]  alloc_workqueue+0x111/0x8e0
[  152.902690][ T8030]  __btrfs_alloc_workqueue+0x11e/0x2a0
[  152.903459][ T8030]  btrfs_alloc_workqueue+0x6d/0x1d0
[  152.904198][ T8030]  scrub_workers_get+0x1e8/0x490
[  152.904929][ T8030]  btrfs_scrub_dev+0x1b9/0x9c0
[  152.905599][ T8030]  btrfs_ioctl+0x122c/0x4e50
[  152.906247][ T8030]  __x64_sys_ioctl+0x137/0x190
[  152.906916][ T8030]  do_syscall_64+0x34/0xb0
[  152.907535][ T8030]  entry_SYSCALL_64_after_hwframe+0x44/0xae
[  152.908365][ T8030]
[  152.908688][ T8030] Freed by task 8884:
[  152.909243][ T8030]  kasan_save_stack+0x21/0x50
[  152.909893][ T8030]  kasan_set_track+0x20/0x30
[  152.910541][ T8030]  kasan_set_free_info+0x24/0x40
[  152.911265][ T8030]  __kasan_slab_free+0xf7/0x140
[  152.911964][ T8030]  kfree+0x9e/0x3d0
[  152.912501][ T8030]  alloc_workqueue+0x7d7/0x8e0
[  152.913182][ T8030]  __btrfs_alloc_workqueue+0x11e/0x2a0
[  152.913949][ T8030]  btrfs_alloc_workqueue+0x6d/0x1d0
[  152.914703][ T8030]  scrub_workers_get+0x1e8/0x490
[  152.915402][ T8030]  btrfs_scrub_dev+0x1b9/0x9c0
[  152.916077][ T8030]  btrfs_ioctl+0x122c/0x4e50
[  152.916729][ T8030]  __x64_sys_ioctl+0x137/0x190
[  152.917414][ T8030]  do_syscall_64+0x34/0xb0
[  152.918034][ T8030]  entry_SYSCALL_64_after_hwframe+0x44/0xae
[  152.918872][ T8030]
[  152.919203][ T8030] The buggy address belongs to the object at ffff88810d31bc00
[  152.919203][ T8030]  which belongs to the cache kmalloc-512 of size 512
[  152.921155][ T8030] The buggy address is located 256 bytes inside of
[  152.921155][ T8030]  512-byte region [ffff88810d31bc00, ffff88810d31be00)
[  152.922993][ T8030] The buggy address belongs to the page:
[  152.923800][ T8030] page:ffffea000434c600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10d318
[  152.925249][ T8030] head:ffffea000434c600 order:2 compound_mapcount:0 compound_pincount:0
[  152.926399][ T8030] flags: 0x57ff00000010200(slab|head|node=1|zone=2|lastcpupid=0x7ff)
[  152.927515][ T8030] raw: 057ff00000010200 dead000000000100 dead000000000122 ffff888009c42c80
[  152.928716][ T8030] raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
[  152.929890][ T8030] page dumped because: kasan: bad access detected
[  152.930759][ T8030]
[  152.931076][ T8030] Memory state around the buggy address:
[  152.931851][ T8030]  ffff88810d31bc00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[  152.932967][ T8030]  ffff88810d31bc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[  152.934068][ T8030] >ffff88810d31bd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[  152.935189][ T8030]                    ^
[  152.935763][ T8030]  ffff88810d31bd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[  152.936847][ T8030]  ffff88810d31be00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[  152.937940][ T8030] ==================================================================

If apply_wqattrs_prepare() fails in alloc_workqueue(), it will call put_pwq()
which invoke a work queue to call pwq_unbound_release_workfn() and use the 'wq'.
The 'wq' allocated in alloc_workqueue() will be freed in error path when
apply_wqattrs_prepare() fails. So it will lead a UAF.

CPU0                                          CPU1
alloc_workqueue()
alloc_and_link_pwqs()
apply_wqattrs_prepare() fails
apply_wqattrs_cleanup()
schedule_work(&pwq->unbound_release_work)
kfree(wq)
                                              worker_thread()
                                              pwq_unbound_release_workfn() <- trigger uaf here

If apply_wqattrs_prepare() fails, the new pwq are not linked, it doesn't
hold any reference to the 'wq', 'wq' is invalid to access in the worker,
so add check pwq if linked to fix this.

Fixes: 2d5f0764b5 ("workqueue: split apply_workqueue_attrs() into 3 stages")
Cc: stable@vger.kernel.org # v4.2+
Reported-by: Hulk Robot <hulkci@huawei.com>
Suggested-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Tested-by: Pavel Skripkin <paskripkin@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
2021-07-21 06:42:31 -10:00
arch ARM: SoC fixes for v5.14 2021-07-17 15:58:24 -07:00
block block-5.14-2021-07-08 2021-07-09 12:05:33 -07:00
certs Kbuild updates for v5.13 (2nd) 2021-05-08 10:00:11 -07:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2021-07-09 11:00:44 -07:00
Documentation Kbuild fixes for v5.14 2021-07-18 11:10:30 -07:00
drivers ARM: SoC fixes for v5.14 2021-07-17 15:58:24 -07:00
fs seq_file: disallow extremely large seq buffer allocations 2021-07-19 17:18:48 -07:00
include ARM: SoC fixes for v5.14 2021-07-17 15:58:24 -07:00
init Revert "mm/slub: use stackdepot to save stack trace in objects" 2021-07-17 13:27:00 -07:00
ipc Merge branch 'akpm' (patches from Andrew) 2021-07-02 12:08:10 -07:00
kernel workqueue: fix UAF in pwq_unbound_release_workfn() 2021-07-21 06:42:31 -10:00
lib lib/test_hmm: remove set but unused page variable 2021-07-15 10:13:49 -07:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm Revert "mm/slub: use stackdepot to save stack trace in objects" 2021-07-17 13:27:00 -07:00
net Networking fixes for 5.14-rc2, including fixes from bpf and netfilter. 2021-07-14 09:24:32 -07:00
samples Networking fixes for 5.14-rc2, including fixes from bpf and netfilter. 2021-07-14 09:24:32 -07:00
scripts Kbuild fixes for v5.14 2021-07-18 11:10:30 -07:00
security asm-generic/unaligned: Unify asm/unaligned.h around struct helper 2021-07-02 12:43:40 -07:00
sound ASoC: Mediatek: MT8183: Fix fall-through warning for Clang 2021-07-13 14:58:18 -05:00
tools perf tools fixes for v5.14: 1st batch 2021-07-18 12:20:27 -07:00
usr .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
virt * Allow again loading KVM on 32-bit non-PAE builds 2021-07-15 11:56:07 -07:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap m68k updates for v5.14 2021-06-28 14:01:03 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: move Murali Karicheri to credits 2021-04-29 15:47:30 -07:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS IOMMU Fixes for Linux v5.14-rc1 2021-07-15 11:50:15 -07:00
Makefile Linux 5.14-rc2 2021-07-18 14:13:49 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.