Re: [syzbot] KASAN: use-after-free Read in task_work_run (2)

[Dmitry Vyukov]

On Wed, 26 Oct 2022 at 20:29, syzbot
<syzbot+9228d6098455bb209ec8@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> syzbot has found a reproducer for the following issue on:
>
> HEAD commit:    88619e77b33d net: stmmac: rk3588: Allow multiple gmac cont..
> git tree:       bpf
> console output: https://syzkaller.appspot.com/x/log.txt?x=1646d6f2880000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=a66c6c673fb555e8
> dashboard link: https://syzkaller.appspot.com/bug?extid=9228d6098455bb209ec8
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12bc425e880000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1126516e880000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/f8435d5c2c21/disk-88619e77.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/551d8a013e81/vmlinux-88619e77.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/7d3f5c29064d/bzImage-88619e77.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+9228d6098455bb209ec8@xxxxxxxxxxxxxxxxxxxxxxxxx

Should perf task work hold a reference to the event to prevent this?

> ==================================================================
> BUG: KASAN: use-after-free in task_work_run+0x1b0/0x270 kernel/task_work.c:178
> Read of size 8 at addr ffff8880752b1c18 by task syz-executor361/3766
>
> CPU: 0 PID: 3766 Comm: syz-executor361 Not tainted 6.1.0-rc2-syzkaller-00073-g88619e77b33d #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
>  print_address_description mm/kasan/report.c:284 [inline]
>  print_report+0x15e/0x45d mm/kasan/report.c:395
>  kasan_report+0xbb/0x1f0 mm/kasan/report.c:495
>  task_work_run+0x1b0/0x270 kernel/task_work.c:178
>  exit_task_work include/linux/task_work.h:38 [inline]
>  do_exit+0xb35/0x2a20 kernel/exit.c:820
>  do_group_exit+0xd0/0x2a0 kernel/exit.c:950
>  get_signal+0x21a1/0x2430 kernel/signal.c:2858
>  arch_do_signal_or_restart+0x82/0x2300 arch/x86/kernel/signal.c:869
>  exit_to_user_mode_loop kernel/entry/common.c:168 [inline]
>  exit_to_user_mode_prepare+0x15f/0x250 kernel/entry/common.c:203
>  __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
>  syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:296
>  do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x7fb9f674b089
> Code: Unable to access opcode bytes at 0x7fb9f674b05f.
> RSP: 002b:00007fb9f66fb318 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
> RAX: 0000000000000001 RBX: 00007fb9f67da1a8 RCX: 00007fb9f674b089
> RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00007fb9f67da1ac
> RBP: 00007fb9f67da1a0 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000003100000400
> R13: 00007fff658570cf R14: 00007fb9f66fb400 R15: 0000000000022000
>  </TASK>
>
> Allocated by task 3766:
>  kasan_save_stack+0x1e/0x40 mm/kasan/common.c:45
>  kasan_set_track+0x21/0x30 mm/kasan/common.c:52
>  __kasan_slab_alloc+0x7e/0x80 mm/kasan/common.c:325
>  kasan_slab_alloc include/linux/kasan.h:201 [inline]
>  slab_post_alloc_hook mm/slab.h:737 [inline]
>  slab_alloc_node mm/slub.c:3398 [inline]
>  kmem_cache_alloc_node+0x2fc/0x400 mm/slub.c:3443
>  perf_event_alloc.part.0+0x69/0x3bc0 kernel/events/core.c:11625
>  perf_event_alloc kernel/events/core.c:12174 [inline]
>  __do_sys_perf_event_open+0x4ae/0x32d0 kernel/events/core.c:12272
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
> Freed by task 0:
>  kasan_save_stack+0x1e/0x40 mm/kasan/common.c:45
>  kasan_set_track+0x21/0x30 mm/kasan/common.c:52
>  kasan_save_free_info+0x2a/0x40 mm/kasan/generic.c:511
>  ____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:177 [inline]
>  slab_free_hook mm/slub.c:1724 [inline]
>  slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1750
>  slab_free mm/slub.c:3661 [inline]
>  kmem_cache_free+0xea/0x5b0 mm/slub.c:3683
>  rcu_do_batch kernel/rcu/tree.c:2250 [inline]
>  rcu_core+0x81f/0x1980 kernel/rcu/tree.c:2510
>  __do_softirq+0x1f7/0xad8 kernel/softirq.c:571
>
> Last potentially related work creation:
>  kasan_save_stack+0x1e/0x40 mm/kasan/common.c:45
>  __kasan_record_aux_stack+0xbc/0xd0 mm/kasan/generic.c:481
>  call_rcu+0x99/0x820 kernel/rcu/tree.c:2798
>  put_event kernel/events/core.c:5095 [inline]
>  perf_event_release_kernel+0x6f2/0x940 kernel/events/core.c:5210
>  perf_release+0x33/0x40 kernel/events/core.c:5220
>  __fput+0x27c/0xa90 fs/file_table.c:320
>  task_work_run+0x16b/0x270 kernel/task_work.c:179
>  resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
>  exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
>  exit_to_user_mode_prepare+0x23c/0x250 kernel/entry/common.c:203
>  __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
>  syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:296
>  do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
> Second to last potentially related work creation:
>  kasan_save_stack+0x1e/0x40 mm/kasan/common.c:45
>  __kasan_record_aux_stack+0xbc/0xd0 mm/kasan/generic.c:481
>  task_work_add+0x7b/0x2c0 kernel/task_work.c:48
>  event_sched_out+0xe35/0x1190 kernel/events/core.c:2294
>  __perf_remove_from_context+0x87/0xc40 kernel/events/core.c:2359
>  event_function+0x29e/0x3e0 kernel/events/core.c:254
>  remote_function kernel/events/core.c:92 [inline]
>  remote_function+0x11e/0x1a0 kernel/events/core.c:72
>  __flush_smp_call_function_queue+0x205/0x9a0 kernel/smp.c:630
>  __sysvec_call_function_single+0xca/0x4d0 arch/x86/kernel/smp.c:248
>  sysvec_call_function_single+0x8e/0xc0 arch/x86/kernel/smp.c:243
>  asm_sysvec_call_function_single+0x16/0x20 arch/x86/include/asm/idtentry.h:657
>
> The buggy address belongs to the object at ffff8880752b17c0
>  which belongs to the cache perf_event of size 1392
> The buggy address is located 1112 bytes inside of
>  1392-byte region [ffff8880752b17c0, ffff8880752b1d30)
>
> The buggy address belongs to the physical page:
> page:ffffea0001d4ac00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x752b0
> head:ffffea0001d4ac00 order:3 compound_mapcount:0 compound_pincount:0
> flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
> raw: 00fff00000010200 0000000000000000 dead000000000122 ffff8880118c23c0
> raw: 0000000000000000 0000000080150015 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
> page_owner tracks the page as allocated
> page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 3754, tgid 3753 (syz-executor361), ts 58662170660, free_ts 58383135648
>  prep_new_page mm/page_alloc.c:2538 [inline]
>  get_page_from_freelist+0x10b5/0x2d50 mm/page_alloc.c:4287
>  __alloc_pages+0x1c7/0x5a0 mm/page_alloc.c:5554
>  alloc_pages+0x1a6/0x270 mm/mempolicy.c:2285
>  alloc_slab_page mm/slub.c:1794 [inline]
>  allocate_slab+0x213/0x300 mm/slub.c:1939
>  new_slab mm/slub.c:1992 [inline]
>  ___slab_alloc+0xa91/0x1400 mm/slub.c:3180
>  __slab_alloc.constprop.0+0x56/0xa0 mm/slub.c:3279
>  slab_alloc_node mm/slub.c:3364 [inline]
>  kmem_cache_alloc_node+0x189/0x400 mm/slub.c:3443
>  perf_event_alloc.part.0+0x69/0x3bc0 kernel/events/core.c:11625
>  perf_event_alloc kernel/events/core.c:12174 [inline]
>  __do_sys_perf_event_open+0x4ae/0x32d0 kernel/events/core.c:12272
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x35/0xb0 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:1458 [inline]
>  free_pcp_prepare+0x65c/0xd90 mm/page_alloc.c:1508
>  free_unref_page_prepare mm/page_alloc.c:3386 [inline]
>  free_unref_page+0x19/0x4d0 mm/page_alloc.c:3482
>  __unfreeze_partials+0x17c/0x1a0 mm/slub.c:2586
>  qlink_free mm/kasan/quarantine.c:168 [inline]
>  qlist_free_all+0x6a/0x170 mm/kasan/quarantine.c:187
>  kasan_quarantine_reduce+0x180/0x200 mm/kasan/quarantine.c:294
>  __kasan_slab_alloc+0x62/0x80 mm/kasan/common.c:302
>  kasan_slab_alloc include/linux/kasan.h:201 [inline]
>  slab_post_alloc_hook mm/slab.h:737 [inline]
>  slab_alloc_node mm/slub.c:3398 [inline]
>  slab_alloc mm/slub.c:3406 [inline]
>  __kmem_cache_alloc_lru mm/slub.c:3413 [inline]
>  kmem_cache_alloc+0x2ac/0x3c0 mm/slub.c:3422
>  kmem_cache_zalloc include/linux/slab.h:702 [inline]
>  alloc_buffer_head+0x20/0x140 fs/buffer.c:2899
>  alloc_page_buffers+0x280/0x790 fs/buffer.c:829
>  create_empty_buffers+0x2c/0xf20 fs/buffer.c:1543
>  ext4_block_write_begin+0x10a7/0x15f0 fs/ext4/inode.c:1074
>  ext4_da_write_begin+0x44c/0xb50 fs/ext4/inode.c:3003
>  generic_perform_write+0x252/0x570 mm/filemap.c:3753
>  ext4_buffered_write_iter+0x15b/0x460 fs/ext4/file.c:285
>  ext4_file_write_iter+0x8b8/0x16e0 fs/ext4/file.c:700
>  __kernel_write_iter+0x25e/0x730 fs/read_write.c:517
>
> Memory state around the buggy address:
>  ffff8880752b1b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8880752b1b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >ffff8880752b1c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                             ^
>  ffff8880752b1c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8880752b1d00: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
> ==================================================================
>