Re: [syzbot] WARNING in __dma_map_sg_attrs

[Daniel Vetter]

On Sat, Feb 05, 2022 at 12:18:23PM -0800, syzbot wrote:
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    0457e5153e0e Merge tag 'for-linus' of git://git.kernel.org..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=11b2637c700000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=6f043113811433a5
> 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
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11c65542700000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1163f480700000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+10e27961f4da37c443b2@xxxxxxxxxxxxxxxxxxxxxxxxx

Adding Gerd, since this seems to blow up in udmabuf.

I wonder why syzbot didn't figure this out, since it seems to have
correctly added both dma-api and dma-buf people. Just not the maintainer
for the begin_cpu_udmabuf function in the middle of the backtrace?
-Daniel

> 

> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 3595 at kernel/dma/mapping.c:188 __dma_map_sg_attrs+0x181/0x1f0 kernel/dma/mapping.c:188
> Modules linked in:
> CPU: 0 PID: 3595 Comm: syz-executor249 Not tainted 5.17.0-rc2-syzkaller-00316-g0457e5153e0e #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> 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 c0 83 b5 0d e9 db fe ff ff e8 b6 0f 13 00 0f 0b e8 af 0f 13 00 <0f> 0b 45 31 e4 e9 54 ff ff ff e8 a0 0f 13 00 49 8d 7f 50 48 b8 00
> RSP: 0018:ffffc90002a07d68 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: ffff88807e25e2c0 RSI: ffffffff81649e91 RDI: ffff88801b848408
> RBP: ffff88801b848000 R08: 0000000000000002 R09: ffff88801d86c74f
> R10: ffffffff81649d72 R11: 0000000000000001 R12: 0000000000000002
> R13: ffff88801d86c680 R14: 0000000000000001 R15: 0000000000000000
> FS:  0000555556e30300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000200000cc CR3: 000000001d74a000 CR4: 00000000003506e0
> 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
>  get_sg_table.isra.0+0xe0/0x160 drivers/dma-buf/udmabuf.c:72
>  begin_cpu_udmabuf+0x130/0x1d0 drivers/dma-buf/udmabuf.c:126
>  dma_buf_begin_cpu_access+0xfd/0x1d0 drivers/dma-buf/dma-buf.c:1164
>  dma_buf_ioctl+0x259/0x2b0 drivers/dma-buf/dma-buf.c:363
>  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: 0033:0x7f62fcf530f9
> 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:00007ffe3edab9b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f62fcf530f9
> RDX: 0000000020000200 RSI: 0000000040086200 RDI: 0000000000000006
> RBP: 00007f62fcf170e0 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007f62fcf17170
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
>  </TASK>
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch