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Date:   Tue, 06 Sep 2022 00:36:26 -0700
Message-ID: <000000000000fad77705e7fd40fb@google.com>
Subject: [syzbot] KASAN: use-after-free Read in task_work_run (2)
From:   syzbot <syzbot+9228d6098455bb209ec8@syzkaller.appspotmail.com>
To:     asml.silence@gmail.com, axboe@kernel.dk, ebiederm@xmission.com,
        keescook@chromium.org, linux-kernel@vger.kernel.org,
        syzkaller-bugs@googlegroups.com
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Hello,

syzbot found the following issue on:

HEAD commit:    c5e4d5e99162 Merge tag 'fscache-fixes-20220831' of git://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=142e0e1b080000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9c5c41fc03fda66f
dashboard link: https://syzkaller.appspot.com/bug?extid=9228d6098455bb209ec8
compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9228d6098455bb209ec8@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in task_work_run+0x126/0x1c0 kernel/task_work.c:176
Read of size 8 at addr ffff88801d1fe500 by task syz-executor.2/18582

CPU: 0 PID: 18582 Comm: syz-executor.2 Not tainted 6.0.0-rc3-syzkaller-00031-gc5e4d5e99162 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
 print_address_description+0x65/0x4b0 mm/kasan/report.c:317
 print_report+0x108/0x220 mm/kasan/report.c:433
 kasan_report+0xfb/0x130 mm/kasan/report.c:495
 task_work_run+0x126/0x1c0 kernel/task_work.c:176
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0x134/0x160 kernel/entry/common.c:169
 exit_to_user_mode_prepare+0xad/0x110 kernel/entry/common.c:201
 __syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]
 syscall_exit_to_user_mode+0x2e/0x60 kernel/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f287f289279
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f28804cd168 EFLAGS: 00000246 ORIG_RAX: 0000000000000119
RAX: 0000000000000001 RBX: 00007f287f39bf80 RCX: 00007f287f289279
RDX: 0000000000000001 RSI: 0000000020000000 RDI: 0000000000000003
RBP: 00007f287f2e32e9 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000000006ff R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffd34f4ba0f R14: 00007f28804cd300 R15: 0000000000022000
 </TASK>

Allocated by task 18586:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:437 [inline]
 __kasan_slab_alloc+0xb2/0xe0 mm/kasan/common.c:470
 kasan_slab_alloc include/linux/kasan.h:224 [inline]
 slab_post_alloc_hook mm/slab.h:727 [inline]
 slab_alloc_node mm/slub.c:3243 [inline]
 slab_alloc mm/slub.c:3251 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3258 [inline]
 kmem_cache_alloc+0x1a6/0x310 mm/slub.c:3268
 kmem_cache_zalloc include/linux/slab.h:723 [inline]
 __alloc_file+0x26/0x230 fs/file_table.c:138
 alloc_empty_file+0xa9/0x1b0 fs/file_table.c:187
 alloc_file+0x58/0x5e0 fs/file_table.c:229
 alloc_file_pseudo+0x260/0x300 fs/file_table.c:272
 dma_buf_getfile drivers/dma-buf/dma-buf.c:534 [inline]
 dma_buf_export+0x634/0x920 drivers/dma-buf/dma-buf.c:652
 drm_gem_dmabuf_export drivers/gpu/drm/drm_prime.c:253 [inline]
 drm_gem_prime_export+0x255/0x400 drivers/gpu/drm/drm_prime.c:895
 export_and_register_object drivers/gpu/drm/drm_prime.c:397 [inline]
 drm_gem_prime_handle_to_fd+0x3e6/0x530 drivers/gpu/drm/drm_prime.c:465
 drm_ioctl_kernel+0x33e/0x4f0 drivers/gpu/drm/drm_ioctl.c:782
 drm_ioctl+0x626/0xa10 drivers/gpu/drm/drm_ioctl.c:885
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Freed by task 18595:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4c/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0xd8/0x120 mm/kasan/common.c:367
 kasan_slab_free include/linux/kasan.h:200 [inline]
 slab_free_hook mm/slub.c:1754 [inline]
 slab_free_freelist_hook+0x12e/0x1a0 mm/slub.c:1780
 slab_free mm/slub.c:3534 [inline]
 kmem_cache_free+0x95/0x1d0 mm/slub.c:3551
 rcu_do_batch kernel/rcu/tree.c:2245 [inline]
 rcu_core+0xa61/0x1710 kernel/rcu/tree.c:2505
 __do_softirq+0x382/0x793 kernel/softirq.c:571

Last potentially related work creation:
 kasan_save_stack+0x3b/0x60 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:348
 call_rcu+0x163/0x9c0 kernel/rcu/tree.c:2793
 task_work_run+0x146/0x1c0 kernel/task_work.c:177
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0x134/0x160 kernel/entry/common.c:169
 exit_to_user_mode_prepare+0xad/0x110 kernel/entry/common.c:201
 __syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]
 syscall_exit_to_user_mode+0x2e/0x60 kernel/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Second to last potentially related work creation:
 kasan_save_stack+0x3b/0x60 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:348
 task_work_add+0x2f/0x200 kernel/task_work.c:48
 fput+0xdc/0x1a0 fs/file_table.c:381
 dma_buf_poll_cb drivers/dma-buf/dma-buf.c:213 [inline]
 dma_buf_poll+0x53a/0x680 drivers/dma-buf/dma-buf.c:295
 vfs_poll include/linux/poll.h:88 [inline]
 ep_item_poll fs/eventpoll.c:853 [inline]
 ep_send_events fs/eventpoll.c:1692 [inline]
 ep_poll+0xb27/0x1e60 fs/eventpoll.c:1821
 do_epoll_wait+0x1a2/0x210 fs/eventpoll.c:2256
 do_epoll_pwait fs/eventpoll.c:2290 [inline]
 __do_sys_epoll_pwait fs/eventpoll.c:2303 [inline]
 __se_sys_epoll_pwait+0x28e/0x480 fs/eventpoll.c:2297
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

The buggy address belongs to the object at ffff88801d1fe500
 which belongs to the cache filp of size 456
The buggy address is located 0 bytes inside of
 456-byte region [ffff88801d1fe500, ffff88801d1fe6c8)

The buggy address belongs to the physical page:
page:ffffea0000747f80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1d1fe
head:ffffea0000747f80 order:1 compound_mapcount:0 compound_pincount:0
memcg:ffff888072449c01
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 ffffea00005ddf80 dead000000000002 ffff888140007a00
raw: 0000000000000000 00000000000c000c 00000001ffffffff ffff888072449c01
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 3111, tgid 3111 (v4l_id), ts 20130623440, free_ts 19733718234
 prep_new_page mm/page_alloc.c:2532 [inline]
 get_page_from_freelist+0x72b/0x7a0 mm/page_alloc.c:4283
 __alloc_pages+0x259/0x560 mm/page_alloc.c:5515
 alloc_slab_page+0x70/0xf0 mm/slub.c:1824
 allocate_slab+0x5e/0x520 mm/slub.c:1969
 new_slab mm/slub.c:2029 [inline]
 ___slab_alloc+0x42e/0xce0 mm/slub.c:3031
 __slab_alloc mm/slub.c:3118 [inline]
 slab_alloc_node mm/slub.c:3209 [inline]
 slab_alloc mm/slub.c:3251 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3258 [inline]
 kmem_cache_alloc+0x25d/0x310 mm/slub.c:3268
 kmem_cache_zalloc include/linux/slab.h:723 [inline]
 __alloc_file+0x26/0x230 fs/file_table.c:138
 alloc_empty_file+0xa9/0x1b0 fs/file_table.c:187
 path_openat+0xf1/0x2e00 fs/namei.c:3677
 do_filp_open+0x275/0x500 fs/namei.c:3718
 do_sys_openat2+0x13b/0x500 fs/open.c:1311
 do_sys_open fs/open.c:1327 [inline]
 __do_sys_openat fs/open.c:1343 [inline]
 __se_sys_openat fs/open.c:1338 [inline]
 __x64_sys_openat+0x243/0x290 fs/open.c:1338
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 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:1449 [inline]
 free_pcp_prepare+0x812/0x900 mm/page_alloc.c:1499
 free_unref_page_prepare mm/page_alloc.c:3380 [inline]
 free_unref_page+0x7d/0x630 mm/page_alloc.c:3476
 qlist_free_all+0x2b/0x70 mm/kasan/quarantine.c:187
 kasan_quarantine_reduce+0x169/0x180 mm/kasan/quarantine.c:294
 __kasan_slab_alloc+0x2f/0xe0 mm/kasan/common.c:447
 kasan_slab_alloc include/linux/kasan.h:224 [inline]
 slab_post_alloc_hook mm/slab.h:727 [inline]
 slab_alloc_node mm/slub.c:3243 [inline]
 slab_alloc mm/slub.c:3251 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3258 [inline]
 kmem_cache_alloc+0x1a6/0x310 mm/slub.c:3268
 vm_area_alloc+0x20/0xe0 kernel/fork.c:459
 mmap_region+0xb4a/0x16f0 mm/mmap.c:1732
 do_mmap+0x7a7/0xdf0 mm/mmap.c:1540
 vm_mmap_pgoff+0x1e5/0x2f0 mm/util.c:552
 ksys_mmap_pgoff+0x48c/0x6d0 mm/mmap.c:1586
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Memory state around the buggy address:
 ffff88801d1fe400: fb fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc
 ffff88801d1fe480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88801d1fe500: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff88801d1fe580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88801d1fe600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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