linux-kernel - Re: [syzbot] [mm?] WARNING in __gup_longterm

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Message-Id: <20230704092451.72974b7a62ae08d48c077e10@linux-foundation.org>
Date:   Tue, 4 Jul 2023 09:24:51 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     syzbot <syzbot+6cf44e127903fdf9d929@...kaller.appspotmail.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        syzkaller-bugs@...glegroups.com,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [syzbot] [mm?] WARNING in __gup_longterm_locked

On Tue, 04 Jul 2023 02:37:56 -0700 syzbot <syzbot+6cf44e127903fdf9d929@...kaller.appspotmail.com> wrote:

> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    f8566aa4f176 Merge tag 'x86-urgent-2023-07-01' of git://gi..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=15ebe50b280000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=7406f415f386e786
> dashboard link: https://syzkaller.appspot.com/bug?extid=6cf44e127903fdf9d929
> 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=12e5b04f280000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=102dff80a80000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/08033ccab6ef/disk-f8566aa4.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/04c5c8c7e53a/vmlinux-f8566aa4.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/942a1c157a92/bzImage-f8566aa4.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+6cf44e127903fdf9d929@...kaller.appspotmail.com
> 
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 5001 at mm/gup.c:1173 __get_user_pages+0xd49/0x1080 mm/gup.c:1173

Thanks.  This is the temporary warning which was added by Linus's
a425ac5365f6cb3cc4 ("gup: add warning if some caller would seem to want
stack expansion").

> Modules linked in:
> CPU: 1 PID: 5001 Comm: syz-executor229 Not tainted 6.4.0-syzkaller-10062-gf8566aa4f176 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
> RIP: 0010:__get_user_pages+0xd49/0x1080 mm/gup.c:1173
> Code: 89 f8 48 c1 e8 03 80 3c 08 00 0f 85 bc 02 00 00 48 8b 44 24 20 48 8b 80 c0 00 00 00 48 8d 1c e8 e9 ad f7 ff ff e8 37 19 c3 ff <0f> 0b e9 32 f6 ff ff e8 2b 19 c3 ff 0f 0b e8 24 19 c3 ff 44 89 ed
> RSP: 0018:ffffc90003a3f558 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: 0000000000000100 RCX: 0000000000000000
> RDX: ffff888020630000 RSI: ffffffff81c1b599 RDI: 0000000000000007
> RBP: 0000000020006000 R08: 0000000000000007 R09: 0000000000000000
> R10: 0000000000000100 R11: 0000000000000001 R12: ffff888018796100
> R13: 0000000000210002 R14: ffff888076f55580 R15: 0000000000000000
> FS:  0000555556272300(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000664740 CR3: 0000000029be1000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  __get_user_pages_locked mm/gup.c:1456 [inline]
>  __gup_longterm_locked+0x6f9/0x23e0 mm/gup.c:2150
>  internal_get_user_pages_fast+0x16e6/0x32f0 mm/gup.c:3148
>  get_user_pages_fast+0xa8/0xf0 mm/gup.c:3226
>  __iov_iter_get_pages_alloc+0x28c/0x1950 lib/iov_iter.c:1111
>  iov_iter_get_pages2+0xa8/0x100 lib/iov_iter.c:1151
>  iter_to_pipe fs/splice.c:1402 [inline]
>  vmsplice_to_pipe fs/splice.c:1492 [inline]
>  __do_sys_vmsplice+0x50c/0xaa0 fs/splice.c:1556
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x7f2a6e4e4b69
> 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:00007ffdb0cc72d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000116
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f2a6e4e4b69
> RDX: 0000000000000001 RSI: 00000000200000c0 RDI: 0000000000000004
> RBP: 00007f2a6e4a8d10 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000001 R11: 0000000000000246 R12: 00007f2a6e4a8da0
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
>  </TASK>
> 
> 
> ---
> 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@...glegroups.com.
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> 
> If the bug is already fixed, let syzbot know by replying with:
> #syz fix: exact-commit-title
> 
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
> 
> If you want to change bug's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
> 
> If the bug is a duplicate of another bug, reply with:
> #syz dup: exact-subject-of-another-report
> 
> If you want to undo deduplication, reply with:
> #syz undup