[syzbot] WARNING in get_vaddr_frames

[syzbot] WARNING in get_vaddr_frames

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    97ee9d1c1696 Merge tag 'block-6.1-2022-12-02' of git://git..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=13ee14ad880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=cc4b2e0a8e8a8366
dashboard link: https://syzkaller.appspot.com/bug?extid=59a71007ccac79e8bb69
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=12e4c55b880000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=129047c3880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/164011fb271c/disk-97ee9d1c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/46378a12aae7/vmlinux-97ee9d1c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/72c541565fa3/bzImage-97ee9d1c.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+59a71007ccac79e8bb69@syzkaller.appspotmail.com

------------[ cut here ]------------
get_vaddr_frames() cannot follow VM_IO mapping
WARNING: CPU: 0 PID: 3635 at drivers/media/common/videobuf2/frame_vector.c:59 get_vaddr_frames drivers/media/common/videobuf2/frame_vector.c:59 [inline]
WARNING: CPU: 0 PID: 3635 at drivers/media/common/videobuf2/frame_vector.c:59 get_vaddr_frames+0x1f2/0x200 drivers/media/common/videobuf2/frame_vector.c:35
Modules linked in:
CPU: 0 PID: 3635 Comm: syz-executor248 Not tainted 6.1.0-rc7-syzkaller-00190-g97ee9d1c1696 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
RIP: 0010:get_vaddr_frames drivers/media/common/videobuf2/frame_vector.c:59 [inline]
RIP: 0010:get_vaddr_frames+0x1f2/0x200 drivers/media/common/videobuf2/frame_vector.c:35
Code: ae 4d fb e9 0b ff ff ff e8 bb ae 4d fb e9 d2 fe ff ff e8 c1 d5 00 fb 48 c7 c7 60 52 1b 8b c6 05 ee 29 bd 07 01 e8 fd c0 27 03 <0f> 0b e9 56 ff ff ff 0f 1f 80 00 00 00 00 41 57 41 56 41 55 41 54
RSP: 0018:ffffc90003c1f820 EFLAGS: 00010286
RAX: 0000000000000000 RBX: ffff88801ff1f000 RCX: 0000000000000000
RDX: ffff8880177f3a80 RSI: ffffffff8165749c RDI: fffff52000783ef6
RBP: ffff88801ff1f004 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000080000000 R11: 0000000000000000 R12: 00000000fffffff2
R13: 0000000000000000 R14: 0000000000000000 R15: ffff888073a41000
FS:  0000555556e79300(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000005d84c8 CR3: 000000002789f000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 vb2_create_framevec+0x59/0xd0 drivers/media/common/videobuf2/videobuf2-memops.c:50
 vb2_vmalloc_get_userptr+0x128/0x520 drivers/media/common/videobuf2/videobuf2-vmalloc.c:88
 __prepare_userptr+0x31e/0x1580 drivers/media/common/videobuf2/videobuf2-core.c:1159
 __buf_prepare+0x5e4/0x780 drivers/media/common/videobuf2/videobuf2-core.c:1401
 vb2_core_prepare_buf+0xe4/0x2c0 drivers/media/common/videobuf2/videobuf2-core.c:1540
 vb2_prepare_buf+0x103/0x170 drivers/media/common/videobuf2/videobuf2-v4l2.c:738
 v4l2_m2m_prepare_buf+0xe8/0x210 drivers/media/v4l2-core/v4l2-mem2mem.c:823
 v4l_prepare_buf drivers/media/v4l2-core/v4l2-ioctl.c:2148 [inline]
 v4l_prepare_buf+0x96/0xc0 drivers/media/v4l2-core/v4l2-ioctl.c:2142
 __video_do_ioctl+0xb9d/0xe20 drivers/media/v4l2-core/v4l2-ioctl.c:3037
 video_usercopy+0x3b8/0x17f0 drivers/media/v4l2-core/v4l2-ioctl.c:3384
 v4l2_ioctl+0x1b7/0x250 drivers/media/v4l2-core/v4l2-dev.c:364
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __x64_sys_ioctl+0x197/0x210 fs/ioctl.c:856
 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: 0033:0x7f4abf6bcc49
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:00007fffe26bf128 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f4abf6bcc49
RDX: 0000000020000300 RSI: 00000000c058565d RDI: 0000000000000003
RBP: 00007f4abf680df0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f4abf680e80
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>


---
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Re: [syzbot] WARNING in get_vaddr_frames

[syzbot]

syzbot has bisected this issue to:

commit 6647e76ab623b2b3fb2efe03a86e9c9046c52c33
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu Dec 1 00:10:52 2022 +0000

    v4l2: don't fall back to follow_pfn() if pin_user_pages_fast() fails

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=115987c5480000
start commit:   e4cf7c25bae5 Merge tag 'kbuild-fixes-v6.2' of git://git.ke..
git tree:       upstream
final oops:     https://syzkaller.appspot.com/x/report.txt?x=135987c5480000
console output: https://syzkaller.appspot.com/x/log.txt?x=155987c5480000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2651619a26b4d687
dashboard link: https://syzkaller.appspot.com/bug?extid=59a71007ccac79e8bb69
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16ee1934480000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=101b997c480000

Reported-by: syzbot+59a71007ccac79e8bb69@syzkaller.appspotmail.com
Fixes: 6647e76ab623 ("v4l2: don't fall back to follow_pfn() if pin_user_pages_fast() fails")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

Re: [syzbot] WARNING in get_vaddr_frames

[Linus Torvalds]

On Sat, Jan 21, 2023 at 12:03 AM syzbot
<syzbot+59a71007ccac79e8bb69@syzkaller.appspotmail.com> wrote:
>
> syzbot has bisected this issue to:
>
> commit 6647e76ab623b2b3fb2efe03a86e9c9046c52c33
> Author: Linus Torvalds <torvalds@linux-foundation.org>
> Date:   Thu Dec 1 00:10:52 2022 +0000
>
>     v4l2: don't fall back to follow_pfn() if pin_user_pages_fast() fails

Yeah, that warning is kind of expected.

> Reported-by: syzbot+59a71007ccac79e8bb69@syzkaller.appspotmail.com
> Fixes: 6647e76ab623 ("v4l2: don't fall back to follow_pfn() if pin_user_pages_fast() fails")

Is there a way to tell syzbot to ignore one particular warning?

Because we could certainly turn it into a pr_warn_once(), but
honestly, if a real use case sees this, I'd rather have the bigger
splat for a while yet.

Then we can remove it entirely (maybe in six months or something?)

                Linus

Re: [syzbot] [media?] WARNING in get_vaddr_frames

[syzbot]

syzbot suspects this issue was fixed by commit:

commit 735de5caf79e06cc9fb96b1b4f4974674ae3e917
Author: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Date:   Thu Aug 17 10:41:32 2023 +0000

    media: vb2: frame_vector.c: replace WARN_ONCE with a comment

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=16c7ad5d680000
start commit:   53663f4103ff Merge tag 'nfs-for-6.5-2' of git://git.linux-..
git tree:       upstream
kernel config:  https://syzkaller.appspot.com/x/.config?x=1b32f62c755c3a9c
dashboard link: https://syzkaller.appspot.com/bug?extid=59a71007ccac79e8bb69
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=178be4b7a80000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=107609a7a80000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: media: vb2: frame_vector.c: replace WARN_ONCE with a comment

For information about bisection process see: https://goo.gl/tpsmEJ#bisection