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In-Reply-To: <20230118222858.3127-1-hdanton@sina.com>
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Subject: Re: [syzbot] KASAN: use-after-free Read in snd_pcm_post_stop
From:   syzbot <syzbot+e29d28728f38190cecfc@syzkaller.appspotmail.com>
To:     hdanton@sina.com, linux-kernel@vger.kernel.org,
        syzkaller-bugs@googlegroups.com
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Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: use-after-free Read in io_fallback_req_func

==================================================================
BUG: KASAN: use-after-free in io_fallback_req_func+0xc7/0x204 io_uring/io_uring.c:251
Read of size 8 at addr ffff888070652948 by task kworker/0:4/5090

CPU: 0 PID: 5090 Comm: kworker/0:4 Not tainted 6.2.0-rc3-next-20230112-syzkaller-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/12/2023
Workqueue: events io_fallback_req_func
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd1/0x138 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:306 [inline]
 print_report+0x15e/0x45d mm/kasan/report.c:417
 kasan_report+0xc0/0xf0 mm/kasan/report.c:517
 io_fallback_req_func+0xc7/0x204 io_uring/io_uring.c:251
 process_one_work+0x9bf/0x1750 kernel/workqueue.c:2293
 worker_thread+0x669/0x1090 kernel/workqueue.c:2440
 kthread+0x2e8/0x3a0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
 </TASK>

Allocated by task 5603:
 kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
 kasan_set_track+0x25/0x30 mm/kasan/common.c:52
 __kasan_slab_alloc+0x7f/0x90 mm/kasan/common.c:325
 kasan_slab_alloc include/linux/kasan.h:186 [inline]
 slab_post_alloc_hook mm/slab.h:769 [inline]
 kmem_cache_alloc_bulk+0x3aa/0x730 mm/slub.c:4033
 __io_alloc_req_refill+0xcc/0x40b io_uring/io_uring.c:1063
 io_alloc_req_refill io_uring/io_uring.h:348 [inline]
 io_submit_sqes.cold+0x7c/0xc2 io_uring/io_uring.c:2414
 __do_sys_io_uring_enter+0x9e4/0x2c10 io_uring/io_uring.c:3436
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Freed by task 9:
 kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
 kasan_set_track+0x25/0x30 mm/kasan/common.c:52
 kasan_save_free_info+0x2e/0x40 mm/kasan/generic.c:518
 ____kasan_slab_free mm/kasan/common.c:236 [inline]
 ____kasan_slab_free+0x160/0x1c0 mm/kasan/common.c:200
 kasan_slab_free include/linux/kasan.h:162 [inline]
 slab_free_hook mm/slub.c:1781 [inline]
 slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1807
 slab_free mm/slub.c:3787 [inline]
 kmem_cache_free+0xec/0x4e0 mm/slub.c:3809
 io_req_caches_free+0x1a9/0x1e6 io_uring/io_uring.c:2744
 io_ring_exit_work+0x2e7/0xc80 io_uring/io_uring.c:2974
 process_one_work+0x9bf/0x1750 kernel/workqueue.c:2293
 worker_thread+0x669/0x1090 kernel/workqueue.c:2440
 kthread+0x2e8/0x3a0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

The buggy address belongs to the object at ffff8880706528c0
 which belongs to the cache io_kiocb of size 224
The buggy address is located 136 bytes inside of
 224-byte region [ffff8880706528c0, ffff8880706529a0)

The buggy address belongs to the physical page:
page:ffffea0001c19480 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x70652
memcg:ffff888026aa6301
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 ffff888146499780 dead000000000122 0000000000000000
raw: 0000000000000000 00000000800c000c 00000001ffffffff ffff888026aa6301
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY), pid 5603, tgid 5602 (syz-executor.0), ts 88591275349, free_ts 64543666654
 prep_new_page mm/page_alloc.c:2549 [inline]
 get_page_from_freelist+0x11bb/0x2d50 mm/page_alloc.c:4324
 __alloc_pages+0x1cb/0x5c0 mm/page_alloc.c:5590
 alloc_pages+0x1aa/0x270 mm/mempolicy.c:2281
 alloc_slab_page mm/slub.c:1851 [inline]
 allocate_slab+0x25f/0x350 mm/slub.c:1998
 new_slab mm/slub.c:2051 [inline]
 ___slab_alloc+0xa91/0x1400 mm/slub.c:3193
 __kmem_cache_alloc_bulk mm/slub.c:3951 [inline]
 kmem_cache_alloc_bulk+0x23d/0x730 mm/slub.c:4026
 __io_alloc_req_refill+0xcc/0x40b io_uring/io_uring.c:1063
 io_alloc_req_refill io_uring/io_uring.h:348 [inline]
 io_submit_sqes.cold+0x7c/0xc2 io_uring/io_uring.c:2414
 __do_sys_io_uring_enter+0x9e4/0x2c10 io_uring/io_uring.c:3436
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1451 [inline]
 __free_pages_ok+0x6ac/0xdc0 mm/page_alloc.c:1707
 kvfree+0x46/0x50 mm/util.c:649
 wg_destruct+0x2f4/0x400 drivers/net/wireguard/device.c:265
 netdev_run_todo+0x6bf/0x1100 net/core/dev.c:10352
 default_device_exit_batch+0x456/0x590 net/core/dev.c:11349
 ops_exit_list+0x125/0x170 net/core/net_namespace.c:174
 cleanup_net+0x4ee/0xb10 net/core/net_namespace.c:606
 process_one_work+0x9bf/0x1750 kernel/workqueue.c:2293
 worker_thread+0x669/0x1090 kernel/workqueue.c:2440
 kthread+0x2e8/0x3a0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

Memory state around the buggy address:
 ffff888070652800: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff888070652880: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
>ffff888070652900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff888070652980: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888070652a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


Tested on:

commit:         0a093b28 Add linux-next specific files for 20230112
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=151c52a9480000
kernel config:  https://syzkaller.appspot.com/x/.config?x=835f3591019836d5
dashboard link: https://syzkaller.appspot.com/bug?extid=e29d28728f38190cecfc
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
patch:          https://syzkaller.appspot.com/x/patch.diff?x=14f99661480000