Re: kernel BUG at include/linux/mm.h:LINE! (4)

[Eric Biggers]

On Fri, Mar 01, 2019 at 11:05:05PM -0800, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    42fd8df9d1d9 Add linux-next specific files for 20190228
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=16c3cd5cc00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=c0f38652d28b522f
> dashboard link: https://syzkaller.appspot.com/bug?extid=cc252aa9d2d3b576246f
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> 
> Unfortunately, I don't have any reproducer for this crash yet.
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+cc252aa9d2d3b576246f@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> page dumped because: VM_BUG_ON_PAGE(page_ref_count(page) == 0)
> page->mem_cgroup:ffff888059786cc0
> ------------[ cut here ]------------
> kernel BUG at include/linux/mm.h:579!
> invalid opcode: 0000 [#1] PREEMPT SMP KASAN
> CPU: 0 PID: 22405 Comm: syz-executor.3 Not tainted 5.0.0-rc8-next-20190228
> #45
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010:put_page_testzero include/linux/mm.h:579 [inline]
> RIP: 0010:put_page include/linux/mm.h:1025 [inline]
> RIP: 0010:generic_pipe_buf_release+0x120/0x160 fs/pipe.c:224
> Code: bd ff 4c 89 e7 e8 90 43 db ff e8 5b 07 bd ff 5b 41 5c 41 5d 5d c3 e8
> 4f 07 bd ff 48 c7 c6 60 98 75 87 4c 89 e7 e8 c0 db e4 ff <0f> 0b e8 39 07 bd
> ff 4d 8d 65 ff e9 3d ff ff ff 48 89 df e8 e8 f8
> RSP: 0018:ffff888056c57920 EFLAGS: 00010246
> RAX: 0000000000040000 RBX: ffffea0002283db4 RCX: ffffc9000c456000
> RDX: 0000000000040000 RSI: ffffffff81984e72 RDI: ffffed100ad8af08
> RBP: ffff888056c57938 R08: 0000000000000021 R09: ffffed1015d05011
> R10: ffffed1015d05010 R11: ffff8880ae828087 R12: ffffea0002283d80
> R13: 0000000000000000 R14: ffff88809ad3c800 R15: ffff8880592ac928
> FS:  00007fb53aaf2700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fff65e0fdb8 CR3: 0000000093a2f000 CR4: 00000000001406f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  pipe_buf_release include/linux/pipe_fs_i.h:129 [inline]
>  iter_file_splice_write+0x7d1/0xbe0 fs/splice.c:759
>  do_splice_from fs/splice.c:847 [inline]
>  direct_splice_actor+0x126/0x1a0 fs/splice.c:1019
>  splice_direct_to_actor+0x369/0x970 fs/splice.c:974
>  do_splice_direct+0x1da/0x2a0 fs/splice.c:1062
>  do_sendfile+0x597/0xd00 fs/read_write.c:1442
>  __do_sys_sendfile64 fs/read_write.c:1503 [inline]
>  __se_sys_sendfile64 fs/read_write.c:1489 [inline]
>  __x64_sys_sendfile64+0x1dd/0x220 fs/read_write.c:1489
>  do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x457e29
> Code: ad b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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
> 0f 83 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007fb53aaf1c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
> RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000457e29
> RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000000000000003
> RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000102000000 R11: 0000000000000246 R12: 00007fb53aaf26d4
> R13: 00000000004c4dce R14: 00000000004d8af8 R15: 00000000ffffffff
> Modules linked in:
> ---[ end trace ce17ea3937b628f2 ]---
> RIP: 0010:put_page_testzero include/linux/mm.h:579 [inline]
> RIP: 0010:put_page include/linux/mm.h:1025 [inline]
> RIP: 0010:generic_pipe_buf_release+0x120/0x160 fs/pipe.c:224
> Code: bd ff 4c 89 e7 e8 90 43 db ff e8 5b 07 bd ff 5b 41 5c 41 5d 5d c3 e8
> 4f 07 bd ff 48 c7 c6 60 98 75 87 4c 89 e7 e8 c0 db e4 ff <0f> 0b e8 39 07 bd
> ff 4d 8d 65 ff e9 3d ff ff ff 48 89 df e8 e8 f8
> RSP: 0018:ffff888056c57920 EFLAGS: 00010246
> RAX: 0000000000040000 RBX: ffffea0002283db4 RCX: ffffc9000c456000
> RDX: 0000000000040000 RSI: ffffffff81984e72 RDI: ffffed100ad8af08
> RBP: ffff888056c57938 R08: 0000000000000021 R09: ffffed1015d05011
> R10: ffffed1015d05010 R11: ffff8880ae828087 R12: ffffea0002283d80
> R13: 0000000000000000 R14: ffff88809ad3c800 R15: ffff8880592ac928
> FS:  00007fb53aaf2700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000001b30225000 CR3: 0000000093a2f000 CR4: 00000000001406e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> 
> 
> ---
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Well it's probably the same as this:
https://groups.google.com/forum/#!topic/syzkaller-bugs/GTzYqK1FaPI, just
reported a day too late as it was already fixed in next-20190301 by the change
folded into "block: introduce mp_bvec_for_each_page() for iterating over page".

#syz invalid

Also Dmitry, I thought that syzbot is only supposed to report bugs on linux-next
when they have a reproducer?

- Eric