Re: [syzbot] KASAN: use-after-free Read in create_worker_cb

[Jens Axboe]

On 3/29/21 1:54 PM, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    93129492 Add linux-next specific files for 20210326
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=144509bad00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=4c9322cd4e3b7a16
> dashboard link: https://syzkaller.appspot.com/bug?extid=099593561bbd1805b839
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=124ce00ed00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1664d5aad00000
> 
> The issue was bisected to:
> 
> commit 4d004099a668c41522242aa146a38cc4eb59cb1e
> Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Date:   Fri Oct 2 09:04:21 2020 +0000
> 
>     lockdep: Fix lockdep recursion
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=12f96b7cd00000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=11f96b7cd00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=16f96b7cd00000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+099593561bbd1805b839@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: 4d004099a668 ("lockdep: Fix lockdep recursion")
> 
> ==================================================================
> BUG: KASAN: use-after-free in create_worker_cb+0xaa/0xc0 fs/io-wq.c:272
> Read of size 8 at addr ffff88801bf150e8 by task syz-executor364/8509
> 
> CPU: 0 PID: 8509 Comm: syz-executor364 Not tainted 5.12.0-rc4-next-20210326-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:79 [inline]
>  dump_stack+0x141/0x1d7 lib/dump_stack.c:120
>  print_address_description.constprop.0.cold+0x5b/0x2f8 mm/kasan/report.c:232
>  __kasan_report mm/kasan/report.c:399 [inline]
>  kasan_report.cold+0x7c/0xd8 mm/kasan/report.c:416
>  create_worker_cb+0xaa/0xc0 fs/io-wq.c:272
>  task_work_run+0xdd/0x1a0 kernel/task_work.c:143
>  exit_task_work include/linux/task_work.h:30 [inline]
>  do_exit+0xbfc/0x2a60 kernel/exit.c:825
>  do_group_exit+0x125/0x310 kernel/exit.c:922
>  __do_sys_exit_group kernel/exit.c:933 [inline]
>  __se_sys_exit_group kernel/exit.c:931 [inline]
>  __x64_sys_exit_group+0x3a/0x50 kernel/exit.c:931
>  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x447359
> Code: Unable to access opcode bytes at RIP 0x44732f.
> RSP: 002b:00007ffdfb4e3ea8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
> RAX: ffffffffffffffda RBX: 00000000004b8390 RCX: 0000000000447359
> RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000
> RBP: 0000000000000000 R08: ffffffffffffffc0 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004b8390
> R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000001
> 
> Allocated by task 8509:
>  kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
>  kasan_set_track mm/kasan/common.c:46 [inline]
>  set_alloc_info mm/kasan/common.c:428 [inline]
>  ____kasan_kmalloc mm/kasan/common.c:507 [inline]
>  ____kasan_kmalloc mm/kasan/common.c:466 [inline]
>  __kasan_kmalloc+0x9b/0xd0 mm/kasan/common.c:516
>  kmalloc_node include/linux/slab.h:574 [inline]
>  kzalloc_node include/linux/slab.h:697 [inline]
>  io_wq_create+0x6e4/0xca0 fs/io-wq.c:934
>  io_init_wq_offload fs/io_uring.c:7938 [inline]
>  io_uring_alloc_task_context+0x1bf/0x660 fs/io_uring.c:7957
>  __io_uring_add_task_file+0x29a/0x3c0 fs/io_uring.c:8915
>  io_uring_add_task_file fs/io_uring.c:8951 [inline]
>  io_uring_install_fd fs/io_uring.c:9509 [inline]
>  io_uring_create fs/io_uring.c:9656 [inline]
>  io_uring_setup+0x20dd/0x2b00 fs/io_uring.c:9693
>  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> Freed by task 8509:
>  kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
>  kasan_set_track+0x1c/0x30 mm/kasan/common.c:46
>  kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:357
>  ____kasan_slab_free mm/kasan/common.c:360 [inline]
>  ____kasan_slab_free mm/kasan/common.c:325 [inline]
>  __kasan_slab_free+0xfb/0x130 mm/kasan/common.c:368
>  kasan_slab_free include/linux/kasan.h:212 [inline]
>  slab_free_hook mm/slub.c:1578 [inline]
>  slab_free_freelist_hook+0xdf/0x240 mm/slub.c:1603
>  slab_free mm/slub.c:3163 [inline]
>  kfree+0xe5/0x7f0 mm/slub.c:4230
>  io_wq_destroy+0x13e/0x2d0 fs/io-wq.c:1022
>  io_wq_put fs/io-wq.c:1032 [inline]
>  io_wq_put_and_exit+0x7a/0xa0 fs/io-wq.c:1038
>  io_uring_clean_tctx+0xed/0x160 fs/io_uring.c:8988
>  __io_uring_files_cancel+0x703/0x850 fs/io_uring.c:9053
>  io_uring_files_cancel include/linux/io_uring.h:22 [inline]
>  do_exit+0x299/0x2a60 kernel/exit.c:780
>  do_group_exit+0x125/0x310 kernel/exit.c:922
>  __do_sys_exit_group kernel/exit.c:933 [inline]
>  __se_sys_exit_group kernel/exit.c:931 [inline]
>  __x64_sys_exit_group+0x3a/0x50 kernel/exit.c:931
>  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> The buggy address belongs to the object at ffff88801bf15000
>  which belongs to the cache kmalloc-1k of size 1024
> The buggy address is located 232 bytes inside of
>  1024-byte region [ffff88801bf15000, ffff88801bf15400)
> The buggy address belongs to the page:
> page:ffffea00006fc400 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88801bf15800 pfn:0x1bf10
> head:ffffea00006fc400 order:3 compound_mapcount:0 compound_pincount:0
> flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
> raw: 00fff00000010200 ffffea00004cd808 ffff888010840888 ffff888010841dc0
> raw: ffff88801bf15800 000000000010000d 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
>  ffff88801bf14f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>  ffff88801bf15000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>> ffff88801bf15080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                                                           ^
>  ffff88801bf15100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff88801bf15180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================

#syz test: git://git.kernel.dk/linux-block for-5.13/io_uring

-- 
Jens Axboe