Re: [syzbot] WARNING in __dma_map_sg_attrs

[Christoph Hellwig]

This means the virtgpu driver uses dma mapping helpers but has not set up
a DMA mask (which most likely suggests it is some kind of virtual device).

On Wed, Dec 01, 2021 at 10:18:21AM -0800, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    c5c17547b778 Merge tag 'net-5.16-rc3' of git://git.kernel...
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=13a73609b00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=bf85c53718a1e697
> dashboard link: https://syzkaller.appspot.com/bug?extid=10e27961f4da37c443b2
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+10e27961f4da37c443b2@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> ------------[ cut here ]------------
> WARNING: CPU: 2 PID: 17169 at kernel/dma/mapping.c:188 __dma_map_sg_attrs+0x181/0x1f0 kernel/dma/mapping.c:188
> Modules linked in:
> CPU: 0 PID: 17169 Comm: syz-executor.3 Not tainted 5.16.0-rc2-syzkaller #0
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
> RIP: 0010:__dma_map_sg_attrs+0x181/0x1f0 kernel/dma/mapping.c:188
> Code: 00 00 00 00 00 fc ff df 48 c1 e8 03 80 3c 10 00 75 71 4c 8b 3d 70 6d b1 0d e9 db fe ff ff e8 86 ff 12 00 0f 0b e8 7f ff 12 00 <0f> 0b 45 31 e4 e9 54 ff ff ff e8 70 ff 12 00 49 8d 7f 50 48 b8 00
> RSP: 0018:ffffc90002c0fb20 EFLAGS: 00010216
> RAX: 0000000000013018 RBX: 0000000000000020 RCX: ffffc900037d4000
> RDX: 0000000000040000 RSI: ffffffff8163d361 RDI: ffff8880182ae4d0
> RBP: ffff8880182ae088 R08: 0000000000000002 R09: ffff888017ba054f
> R10: ffffffff8163d242 R11: 000000000008808a R12: 0000000000000000
> R13: ffff888024ca5700 R14: 0000000000000001 R15: 0000000000000000
> FS:  00007fa269e34700(0000) GS:ffff88802cb00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000000040c120 CR3: 000000006c77c000 CR4: 0000000000150ee0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  dma_map_sgtable+0x70/0xf0 kernel/dma/mapping.c:264
>  drm_gem_map_dma_buf+0x12a/0x1e0 drivers/gpu/drm/drm_prime.c:633
>  __map_dma_buf drivers/dma-buf/dma-buf.c:675 [inline]
>  dma_buf_map_attachment+0x39a/0x5b0 drivers/dma-buf/dma-buf.c:954
>  drm_gem_prime_import_dev.part.0+0x85/0x220 drivers/gpu/drm/drm_prime.c:939
>  drm_gem_prime_import_dev drivers/gpu/drm/drm_prime.c:982 [inline]
>  drm_gem_prime_import+0xc8/0x200 drivers/gpu/drm/drm_prime.c:982
>  virtgpu_gem_prime_import+0x49/0x150 drivers/gpu/drm/virtio/virtgpu_prime.c:166
>  drm_gem_prime_fd_to_handle+0x21d/0x550 drivers/gpu/drm/drm_prime.c:318
>  drm_prime_fd_to_handle_ioctl+0x9b/0xd0 drivers/gpu/drm/drm_prime.c:374
>  drm_ioctl_kernel+0x27d/0x4e0 drivers/gpu/drm/drm_ioctl.c:782
>  drm_ioctl+0x51e/0x9d0 drivers/gpu/drm/drm_ioctl.c:885
>  vfs_ioctl fs/ioctl.c:51 [inline]
>  __do_sys_ioctl fs/ioctl.c:874 [inline]
>  __se_sys_ioctl fs/ioctl.c:860 [inline]
>  __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
>  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: 0033:0x7fa26c8beae9
> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 bc ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007fa269e34188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 00007fa26c9d1f60 RCX: 00007fa26c8beae9
> RDX: 00000000200004c0 RSI: 00000000c00c642e RDI: 0000000000000005
> RBP: 00007fa26c918f6d R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007ffc0019c51f R14: 00007fa269e34300 R15: 0000000000022000
>  </TASK>
> 
> 
> ---
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> 
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