Re: [syzbot] KASAN: stack-out-of-bounds Read in iov_iter_revert

[Pavel Begunkov]

On 8/12/21 2:43 PM, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    1746f4db5135 Merge tag 'orphans-v5.14-rc6' of git://git.ke..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=111065fa300000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=e3a20bae04b96ccd
> dashboard link: https://syzkaller.appspot.com/bug?extid=9671693590ef5aad8953
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=119dcaf6300000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=120d216e300000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+9671693590ef5aad8953@xxxxxxxxxxxxxxxxxxxxxxxxx

I believe, was already discovered and sent out, let's try v2:

#syz test: https://github.com/isilence/linux.git truncate

> 
> ==================================================================
> BUG: KASAN: stack-out-of-bounds in iov_iter_revert lib/iov_iter.c:1093 [inline]
> BUG: KASAN: stack-out-of-bounds in iov_iter_revert+0x803/0x900 lib/iov_iter.c:1033
> Read of size 8 at addr ffffc9000cf478b0 by task syz-executor673/8439
> 
> CPU: 0 PID: 8439 Comm: syz-executor673 Not tainted 5.14.0-rc5-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:105
>  print_address_description.constprop.0.cold+0xf/0x309 mm/kasan/report.c:233
>  __kasan_report mm/kasan/report.c:419 [inline]
>  kasan_report.cold+0x83/0xdf mm/kasan/report.c:436
>  iov_iter_revert lib/iov_iter.c:1093 [inline]
>  iov_iter_revert+0x803/0x900 lib/iov_iter.c:1033
>  io_write+0x57b/0xed0 fs/io_uring.c:3459
>  io_issue_sqe+0x28c/0x6920 fs/io_uring.c:6181
>  __io_queue_sqe+0x1ac/0xf00 fs/io_uring.c:6464
>  io_queue_sqe fs/io_uring.c:6507 [inline]
>  io_submit_sqe fs/io_uring.c:6662 [inline]
>  io_submit_sqes+0x63ea/0x7bc0 fs/io_uring.c:6778
>  __do_sys_io_uring_enter+0xb03/0x1d40 fs/io_uring.c:9389
>  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+0x44/0xae
> RIP: 0033:0x43f8a9
> Code: 28 c3 e8 1a 15 00 00 66 2e 0f 1f 84 00 00 00 00 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 c0 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffcc6759968 EFLAGS: 00000246 ORIG_RAX: 00000000000001aa
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000043f8a9
> RDX: 0000000000000000 RSI: 00000000000052fe RDI: 0000000000000003
> RBP: 00007ffcc6759988 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffcc6759990
> R13: 0000000000000000 R14: 00000000004ae018 R15: 0000000000400488
> 
> 
> addr ffffc9000cf478b0 is located in stack of task syz-executor673/8439 at offset 152 in frame:
>  io_write+0x0/0xed0 fs/io_uring.c:3335
> 
> this frame has 3 objects:
>  [48, 56) 'iovec'
>  [80, 120) '__iter'
>  [160, 288) 'inline_vecs'
> 
> Memory state around the buggy address:
>  ffffc9000cf47780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>  ffffc9000cf47800: 00 00 00 f1 f1 f1 f1 00 00 00 f2 f2 f2 00 00 00
>> ffffc9000cf47880: 00 00 f2 f2 f2 f2 f2 00 00 00 00 00 00 00 00 00
>                                      ^
>  ffffc9000cf47900: 00 00 00 00 00 00 00 f3 f3 f3 f3 00 00 00 00 00
>  ffffc9000cf47980: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ==================================================================
> 
> 
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.
> 
> syzbot will keep track of this issue. See:
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> syzbot can test patches for this issue, for details see:
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> 

-- 
Pavel Begunkov