Re: [syzbot] WARNING in follow_hugetlb_page

[Andrew Morton]

On Fri, 13 May 2022 09:43:24 -0700 syzbot <syzbot+acf65ca584991f3cc447@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

> syzbot has found a reproducer for the following issue on:

Thanks.

> HEAD commit:    1e1b28b936ae Add linux-next specific files for 20220513
> git tree:       linux-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=174ae715f00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=e4eb3c0c4b289571
> dashboard link: https://syzkaller.appspot.com/bug?extid=acf65ca584991f3cc447
> 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=11531766f00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16ce5a9ef00000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+acf65ca584991f3cc447@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 3611 at mm/hugetlb.c:6250 follow_hugetlb_page+0x1326/0x1c80 mm/hugetlb.c:6250

The try_grab_folio() added by 822951d84684d ("mm/hugetlb: Use
try_grab_folio() instead of try_grab_compound_head()").  That commit
has been there over a month so I guess it's something else.  Does
someone have the time to bisect?

> Modules linked in:
> CPU: 1 PID: 3611 Comm: syz-executor603 Not tainted 5.18.0-rc6-next-20220513-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:follow_hugetlb_page+0x1326/0x1c80 mm/hugetlb.c:6250
> Code: 89 44 24 70 e8 2b 1d b7 ff 48 8b 44 24 70 48 85 c0 0f 84 f1 07 00 00 e8 88 1a b7 ff 48 83 ed 01 e9 09 fb ff ff e8 7a 1a b7 ff <0f> 0b 48 8b 7c 24 30 bb f4 ff ff ff e8 69 74 b8 07 4c 8b a4 24 b8
> RSP: 0018:ffffc90002f6f7e0 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: ffff88801bdd4e00 RCX: 0000000000000000
> RDX: ffff88801e4e3a80 RSI: ffffffff81c38f76 RDI: 0000000000000003
> RBP: ffffea0001fe8680 R08: 0000000000000000 R09: 0000000000000003
> R10: ffffffff81b128fb R11: 0000000000000008 R12: 000000000000001a
> R13: ffff88801bdd4e00 R14: ffff88801bdd5600 R15: 0000000000000019
> FS:  0000555556ad2300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020000458 CR3: 000000001e850000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  __get_user_pages+0x27a/0xfa0 mm/gup.c:1146
>  __get_user_pages_locked mm/gup.c:1365 [inline]
>  __gup_longterm_locked+0x1d5/0xfe0 mm/gup.c:1985
>  pin_user_pages+0x8e/0xe0 mm/gup.c:3118
>  io_sqe_buffer_register+0x254/0x1710 fs/io_uring.c:10537
>  io_sqe_buffers_register.cold+0x28e/0x443 fs/io_uring.c:10664
>  __io_uring_register fs/io_uring.c:12682 [inline]
>  __do_sys_io_uring_register+0xd21/0x1930 fs/io_uring.c:12816
>  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+0x46/0xb0
> RIP: 0033:0x7f5f42760cc9
> Code: 28 c3 e8 2a 14 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:00007fffc3407aa8 EFLAGS: 00000246 ORIG_RAX: 00000000000001ab
> RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007f5f42760cc9
> RDX: 0000000020000380 RSI: 0000000000000000 RDI: 0000000000000004
> RBP: 00007f5f42724e70 R08: 0000000010000000 R09: 0000000000000000
> R10: 0000000000000001 R11: 0000000000000246 R12: 00007f5f42724f00
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
>  </TASK>