Re: [Syzkaller & bisect] There is "notify_change" WARNING in v6.1-rc5 kernel

[Pengfei Xu]

Hi Miklos,

On 2022-11-23 at 11:54:59 +0100, Miklos Szeredi wrote:
> On Thu, Nov 17, 2022 at 12:32 PM Pengfei Xu <pengfei.xu@xxxxxxxxx> wrote:
> >
> > Hi Miklos Szeredi and developer,
> >
> > Greeting!
> >
> > There is "notify_change" WARNING in v6.1-rc5:
> > [   45.378232] ------------[ cut here ]------------
> > [   45.378741] WARNING: CPU: 0 PID: 463 at fs/attr.c:327 notify_change+0x9a1/0xb50
> > [   45.379511] Modules linked in:
> > [   45.379868] CPU: 0 PID: 463 Comm: repro Not tainted 6.1.0-rc5-094226ad94f4 #1
> > [   45.380617] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
> > [   45.381752] RIP: 0010:notify_change+0x9a1/0xb50
> > [   45.382234] Code: 44 89 f6 e8 81 2d cf ff 41 83 fe ff 74 0c c7 45 c4 00 00 00 00 e9 e1 fd ff ff 41 be b5 ff ff ff e9 ea fb ff ff e8 ef 2b cf ff <0f> 0b e9 c2 4
> > [   45.384114] RSP: 0018:ffffc90000ef3b30 EFLAGS: 00010246
> > [   45.384661] RAX: 0000000000000000 RBX: 0000000000004200 RCX: ffffffff8155b451
> > [   45.385389] RDX: 0000000000000000 RSI: ffff88800cd40000 RDI: 0000000000000002
> > [   45.386112] RBP: ffffc90000ef3b90 R08: ffff888009ed2f50 R09: 0101010101010101
> > [   45.386840] R10: ffffc90000ef3bb0 R11: 0000000000005c67 R12: ffffc90000ef3bb8
> > [   45.387568] R13: ffff88800af5ed80 R14: 0000000000000000 R15: ffffffff8385ff40
> > [   45.388312] FS:  00007f914d059700(0000) GS:ffff88807dc00000(0000) knlGS:0000000000000000
> > [   45.389142] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [   45.389727] CR2: 0000000020006000 CR3: 000000000bfc0006 CR4: 0000000000770ef0
> > [   45.390458] PKRU: 55555554
> > [   45.390752] Call Trace:
> > [   45.391015]  <TASK>
> > [   45.391253]  ? write_comp_data+0x2f/0x90
> > [   45.391697]  __file_remove_privs+0x1de/0x240
> > [   45.392181]  ? __file_remove_privs+0x1de/0x240
> > [   45.392671]  ? __sanitizer_cov_trace_pc+0x25/0x60
> > [   45.393181]  ? current_time+0x64/0xb0
> > [   45.393592]  file_modified_flags+0x51/0x160
> > [   45.394055]  file_modified+0x20/0x30
> > [   45.394462]  fuse_file_fallocate+0x53a/0x620
> > [   45.394928]  ? __schedule+0x2e6/0x8f0
> > [   45.395347]  ? fuse_copy_file_range+0xc0/0xc0
> > [   45.395835]  vfs_fallocate+0x336/0x690
> > [   45.396243]  ioctl_preallocate+0xdf/0x110
> > [   45.396677]  do_vfs_ioctl+0xaf9/0xc20
> > [   45.397080]  ? __fget_light+0xb0/0x220
> > [   45.397488]  ? __sanitizer_cov_trace_pc+0x25/0x60
> > [   45.397993]  ? write_comp_data+0x2f/0x90
> > [   45.398419]  __x64_sys_ioctl+0xca/0x160
> > [   45.398836]  do_syscall_64+0x3b/0x90
> > [   45.399235]  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> > [   45.399788] RIP: 0033:0x7f914d17f59d
> > [   45.400182] Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 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 8
> > [   45.402039] RSP: 002b:00007f914d058b28 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> > [   45.402815] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f914d17f59d
> > [   45.403543] RDX: 00000000200001c0 RSI: 0000000040305828 RDI: 0000000000000004
> > [   45.404286] RBP: 00007f914d058e00 R08: 0000000100000001 R09: 0000000000000000
> > [   45.405023] R10: 0000000100000001 R11: 0000000000000246 R12: 00007fff22e7ec4e
> > [   45.405758] R13: 00007fff22e7ec4f R14: 00007fff22e7ece0 R15: 00007f914d059700
> > [   45.406496]  </TASK>
> > [   45.406736] ---[ end trace 0000000000000000 ]---
> >
> > Bisected and found the first bad commit:
> > 4a6f278d4827b59ba26ceae0ff4529ee826aa258
> > "fuse: add file_modified() to fallocate"
> >
> > After only revert this commit, this issue was gone.
> >
> > Kconfig, reproduced code from syzkaller, bisect info is in attached.
> >
> > All detailed info is in link:
> > https://github.com/xupengfe/syzkaller_logs/tree/main/221117_083125_notify_change
> >
> > If you find this info is useful, please add the "Reviewed-by" tag from me.
> 
> Thanks for the report, fix now sent out.
  Great, I'm so glad that it's helpful and there is fixed patch for this
  issue! :)

  Thanks!
  BR.

> 
> Miklos
>