Re: virtiofs: WARN_ON(out_sgs + in_sgs != total_sgs)

[Vivek Goyal]

On Fri, Oct 02, 2020 at 10:44:37PM -0400, Qian Cai wrote:
> On Fri, 2020-10-02 at 12:28 -0400, Qian Cai wrote:
> > Running some fuzzing on virtiofs from a non-privileged user could trigger a
> > warning in virtio_fs_enqueue_req():
> > 
> > WARN_ON(out_sgs + in_sgs != total_sgs);
> 
> Okay, I can reproduce this after running for a few hours:
> 
> out_sgs = 3, in_sgs = 2, total_sgs = 6

Thanks. I can also reproduce it simply by calling.

ioctl(fd, 0x5a004000, buf);

I think following WARN_ON() is not correct.

WARN_ON(out_sgs + in_sgs != total_sgs)

toal_sgs should actually be max sgs. It looks at ap->num_pages and
counts one sg for each page. And it assumes that same number of
pages will be used both for input and output.

But there are no such guarantees. With above ioctl() call, I noticed
we are using 2 pages for input (out_sgs) and one page for output (in_sgs).

So out_sgs=4, in_sgs=3 and total_sgs=8 and warning triggers.

I think total sgs is actually max number of sgs and warning
should probably be.

WARN_ON(out_sgs + in_sgs >  total_sgs)

Stefan, WDYT?

I will send a patch for this.

Thanks
Vivek



> 
> and this time from flush_bg_queue() instead of fuse_simple_request().
> 
> From the log, the last piece of code is:
> 
> ftruncate(fd=186, length=4)
> 
> which is a test file on virtiofs:
> 
> [main]  testfile fd:186 filename:trinity-testfile3 flags:2 fopened:1 fcntl_flags:2000 global:1
> [main]   start: 0x7f47c1199000 size:4KB  name: trinity-testfile3 global:1
> 
> 
> [ 9863.468502] WARNING: CPU: 16 PID: 286083 at fs/fuse/virtio_fs.c:1152 virtio_fs_enqueue_req+0xd36/0xde0 [virtiofs]
> [ 9863.474442] Modules linked in: dlci 8021q garp mrp bridge stp llc ieee802154_socket ieee802154 vsock_loopback vmw_vsock_virtio_transport_common vmw_vsock_vmci_transport vsock mpls_router vmw_vmci ip_tunnel as
> [ 9863.474555]  ata_piix fuse serio_raw libata e1000 sunrpc dm_mirror dm_region_hash dm_log dm_mod
> [ 9863.535805] CPU: 16 PID: 286083 Comm: trinity-c5 Kdump: loaded Not tainted 5.9.0-rc7-next-20201002+ #2
> [ 9863.544368] Hardware name: Red Hat KVM, BIOS 1.14.0-1.module+el8.3.0+7638+07cf13d2 04/01/2014
> [ 9863.550129] RIP: 0010:virtio_fs_enqueue_req+0xd36/0xde0 [virtiofs]
> [ 9863.552998] Code: 60 09 23 d9 e9 44 fa ff ff e8 56 09 23 d9 e9 70 fa ff ff 48 89 cf 48 89 4c 24 08 e8 44 09 23 d9 48 8b 4c 24 08 e9 7c fa ff ff <0f> 0b 48 c7 c7 c0 85 60 c0 44 89 e1 44 89 fa 44 89 ee e8 e3 b7
> [ 9863.561720] RSP: 0018:ffff888a696ef6f8 EFLAGS: 00010202
> [ 9863.565420] RAX: 0000000000000000 RBX: ffff88892e030008 RCX: 0000000000000000
> [ 9863.568735] RDX: 0000000000000005 RSI: 0000000000000000 RDI: ffff888a696ef8ac
> [ 9863.572037] RBP: ffff888a49d03d30 R08: ffffed114d2ddf18 R09: ffff888a696ef8a0
> [ 9863.575383] R10: ffff888a696ef8bf R11: ffffed114d2ddf17 R12: 0000000000000006
> [ 9863.578668] R13: 0000000000000003 R14: 0000000000000002 R15: 0000000000000002
> [ 9863.581971] FS:  00007f47c12f5740(0000) GS:ffff888a7f800000(0000) knlGS:0000000000000000
> [ 9863.585752] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 9863.590232] CR2: 0000000000000000 CR3: 0000000a63570005 CR4: 0000000000770ee0
> [ 9863.594698] DR0: 00007f6642e43000 DR1: 0000000000000000 DR2: 0000000000000000
> [ 9863.598521] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
> [ 9863.601861] PKRU: 55555540
> [ 9863.603173] Call Trace:
> [ 9863.604382]  ? virtio_fs_probe+0x13e0/0x13e0 [virtiofs]
> [ 9863.606838]  ? is_bpf_text_address+0x21/0x30
> [ 9863.608869]  ? kernel_text_address+0x125/0x140
> [ 9863.610962]  ? __kernel_text_address+0xe/0x30
> [ 9863.613117]  ? unwind_get_return_address+0x5f/0xa0
> [ 9863.615427]  ? create_prof_cpu_mask+0x20/0x20
> [ 9863.617435]  ? _raw_write_lock_irqsave+0xe0/0xe0
> [ 9863.619627]  virtio_fs_wake_pending_and_unlock+0x1ea/0x610 [virtiofs]
> [ 9863.622638]  ? queue_request_and_unlock+0x115/0x280 [fuse]
> [ 9863.625224]  flush_bg_queue+0x24c/0x3e0 [fuse]
> [ 9863.627325]  fuse_simple_background+0x3d7/0x6c0 [fuse]
> [ 9863.629735]  fuse_send_writepage+0x173/0x420 [fuse]
> [ 9863.632031]  fuse_flush_writepages+0x1fe/0x330 [fuse]
> [ 9863.634463]  ? make_kgid+0x13/0x20
> [ 9863.636064]  ? fuse_change_attributes_common+0x2de/0x940 [fuse]
> [ 9863.638850]  fuse_do_setattr+0xe84/0x13c0 [fuse]
> [ 9863.641024]  ? migrate_swap_stop+0x8d1/0x920
> [ 9863.643041]  ? fuse_flush_times+0x390/0x390 [fuse]
> [ 9863.645347]  ? avc_has_perm_noaudit+0x390/0x390
> [ 9863.647465]  fuse_setattr+0x197/0x400 [fuse]
> [ 9863.649466]  notify_change+0x744/0xda0
> [ 9863.651247]  ? __down_timeout+0x2a0/0x2a0
> [ 9863.653125]  ? do_truncate+0xe2/0x180
> [ 9863.654854]  do_truncate+0xe2/0x180
> [ 9863.656509]  ? __x64_sys_openat2+0x1c0/0x1c0
> [ 9863.658512]  ? alarm_setitimer+0xa0/0x110
> [ 9863.660418]  do_sys_ftruncate+0x1ee/0x2c0
> [ 9863.662311]  do_syscall_64+0x33/0x40
> [ 9863.663980]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [ 9863.666384] RIP: 0033:0x7f47c0c0878d
> [ 9863.668061] 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 ff ff 73 01 c3 48 8b 0d cb 56 2c 00 f7 d8 64 89 08
> [ 9863.676717] RSP: 002b:00007fff515c2598 EFLAGS: 00000246 ORIG_RAX: 000000000000004d
> [ 9863.680226] RAX: ffffffffffffffda RBX: 000000000000004d RCX: 00007f47c0c0878d
> [ 9863.688055] RDX: 0000000000800000 RSI: 0000000000000004 RDI: 00000000000000ba
> [ 9863.693672] RBP: 000000000000004d R08: 000000000000003a R09: 0000000000000001
> [ 9863.699423] R10: 0000000000000005 R11: 0000000000000246 R12: 0000000000000002
> [ 9863.708897] R13: 00007f47c12cb058 R14: 00007f47c12f56c0 R15: 00007f47c12cb000
> [ 9863.713106] CPU: 16 PID: 286083 Comm: trinity-c5 Kdump: loaded Not tainted 5.9.0-rc7-next-20201002+ #2
> [ 9863.717465] Hardware name: Red Hat KVM, BIOS 1.14.0-1.module+el8.3.0+7638+07cf13d2 04/01/2014
> [ 9863.721389] Call Trace:
> [ 9863.722547]  dump_stack+0x7c/0xa2
> [ 9863.724110]  __warn.cold.13+0xe/0x47
> [ 9863.725804]  ? virtio_fs_enqueue_req+0xd36/0xde0 [virtiofs]
> [ 9863.728427]  report_bug+0x1af/0x260
> [ 9863.730054]  handle_bug+0x44/0x80
> [ 9863.731652]  exc_invalid_op+0x13/0x40
> [ 9863.734911]  asm_exc_invalid_op+0x12/0x20
> [ 9863.736940] RIP: 0010:virtio_fs_enqueue_req+0xd36/0xde0 [virtiofs]
> [ 9863.739833] Code: 60 09 23 d9 e9 44 fa ff ff e8 56 09 23 d9 e9 70 fa ff ff 48 89 cf 48 89 4c 24 08 e8 44 09 23 d9 48 8b 4c 24 08 e9 7c fa ff ff <0f> 0b 48 c7 c7 c0 85 60 c0 44 89 e1 44 89 fa 44 89 ee e8 e3 b7
> [ 9863.748519] RSP: 0018:ffff888a696ef6f8 EFLAGS: 00010202
> [ 9863.750935] RAX: 0000000000000000 RBX: ffff88892e030008 RCX: 0000000000000000
> [ 9863.754247] RDX: 0000000000000005 RSI: 0000000000000000 RDI: ffff888a696ef8ac
> [ 9863.760885] RBP: ffff888a49d03d30 R08: ffffed114d2ddf18 R09: ffff888a696ef8a0
> [ 9863.764814] R10: ffff888a696ef8bf R11: ffffed114d2ddf17 R12: 0000000000000006
> [ 9863.768148] R13: 0000000000000003 R14: 0000000000000002 R15: 0000000000000002
> [ 9863.771492]  ? virtio_fs_probe+0x13e0/0x13e0 [virtiofs]
> [ 9863.773950]  ? is_bpf_text_address+0x21/0x30
> [ 9863.775979]  ? kernel_text_address+0x125/0x140
> [ 9863.778061]  ? __kernel_text_address+0xe/0x30
> [ 9863.780124]  ? unwind_get_return_address+0x5f/0xa0
> [ 9863.782395]  ? create_prof_cpu_mask+0x20/0x20
> [ 9863.784451]  ? _raw_write_lock_irqsave+0xe0/0xe0
> [ 9863.786602]  virtio_fs_wake_pending_and_unlock+0x1ea/0x610 [virtiofs]
> [ 9863.789614]  ? queue_request_and_unlock+0x115/0x280 [fuse]
> [ 9863.792178]  flush_bg_queue+0x24c/0x3e0 [fuse]
> [ 9863.796678]  fuse_simple_background+0x3d7/0x6c0 [fuse]
> [ 9863.802329]  fuse_send_writepage+0x173/0x420 [fuse]
> [ 9863.808342]  fuse_flush_writepages+0x1fe/0x330 [fuse]
> [ 9863.812086]  ? make_kgid+0x13/0x20
> [ 9863.813681]  ? fuse_change_attributes_common+0x2de/0x940 [fuse]
> [ 9863.816465]  fuse_do_setattr+0xe84/0x13c0 [fuse]
> [ 9863.819633]  ? migrate_swap_stop+0x8d1/0x920
> [ 9863.824285]  ? fuse_flush_times+0x390/0x390 [fuse]
> [ 9863.827331]  ? avc_has_perm_noaudit+0x390/0x390
> [ 9863.875278]  fuse_setattr+0x197/0x400 [fuse]
> [ 9863.878496]  notify_change+0x744/0xda0
> [ 9863.880640]  ? __down_timeout+0x2a0/0x2a0
> [ 9863.882960]  ? do_truncate+0xe2/0x180
> [ 9863.886311]  do_truncate+0xe2/0x180
> [ 9863.888392]  ? __x64_sys_openat2+0x1c0/0x1c0
> [ 9863.890418]  ? alarm_setitimer+0xa0/0x110
> [ 9863.894430]  do_sys_ftruncate+0x1ee/0x2c0
> [ 9863.896468]  do_syscall_64+0x33/0x40
> [ 9863.898167]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [ 9863.901089] RIP: 0033:0x7f47c0c0878d
> [ 9863.903447] 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 ff ff 73 01 c3 48 8b 0d cb 56 2c 00 f7 d8 64 89 08
> [ 9863.914356] RSP: 002b:00007fff515c2598 EFLAGS: 00000246 ORIG_RAX: 000000000000004d
> [ 9863.917998] RAX: ffffffffffffffda RBX: 000000000000004d RCX: 00007f47c0c0878d
> [ 9863.921364] RDX: 0000000000800000 RSI: 0000000000000004 RDI: 00000000000000ba
> [ 9863.928285] RBP: 000000000000004d R08: 000000000000003a R09: 0000000000000001
> [ 9863.932523] R10: 0000000000000005 R11: 0000000000000246 R12: 0000000000000002
> [ 9863.935835] R13: 00007f47c12cb058 R14: 00007f47c12f56c0 R15: 00007f47c12cb000
> [ 9863.939183] ---[ end trace f6f5d958c186bcee ]---
>