Re: refcount overflow in 4.4.6-grsec kernel

[Marco Schindler]

Tobias Hunger  gmail.com> writes:

> 
> Hi,
> 
> I updated my archlinux to use a grsec kernel (version 4.4.6). Now I
> get lots of errors from PAX and all backtraces show mention btrfs.
> 
> Is this a known problem? Is there anything I can help to debug this?

I'm seeing the same issue with 4.4.8 on hardened gentoo.
This forum post relates, claiming it's a bug within btrfs.
https://forums.grsecurity.net/viewtopic.php?f=3&t=4392

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refcount overflow in 4.4.6-grsec kernel

[Tobias Hunger]

Hi,

I updated my archlinux to use a grsec kernel (version 4.4.6). Now I
get lots of errors from PAX and all backtraces show mention btrfs.

Is this a known problem? Is there anything I can help to debug this?

This is the dump from the logs:

Apr 11 07:43:36 kernel: PAX: refcount overflow detected in:
pacman:11700, uid/euid: 0/0
Apr 11 07:43:36 kernel: CPU: 1 PID: 11700 Comm: pacman Not tainted
4.4.6.201604021734-1-grsec #1
Apr 11 07:43:36 kernel: Hardware name: LENOVO, BIOS 1.08 03/09/2016
Apr 11 07:43:36 kernel: task: 880524c28a80 ti: 880524c294a8
task.ti: 880524c294a8
Apr 11 07:43:36 kernel: RIP: 0010:[]
[] btrfs_qgroup_reserve_meta+0x73/0x90 [btrfs]
Apr 11 07:43:36 kernel: RSP: 0018:c9000d6e3a90  EFLAGS: 0a06
Apr 11 07:43:36 kernel: RAX:  RBX: 8804fecc5050
RCX: 
Apr 11 07:43:36 kernel: RDX: 880524e708c8 RSI: c9000d6e3a48
RDI: 880524c12d70
Apr 11 07:43:36 kernel: RBP: c9000d6e3aa0 R08: 
R09: 88036cf5d048
Apr 11 07:43:36 kernel: R10: 8803739a0410 R11: 
R12: 00014000
Apr 11 07:43:36 kernel: R13: 8804fecc5050 R14: 0005
R15: 00014000
Apr 11 07:43:36 kernel: FS:  03f0e634c740()
GS:88054144() knlGS:
Apr 11 07:43:36 kernel: CS:  0010 DS:  ES:  CR0: 80050033
Apr 11 07:43:36 kernel: CR2: 0074a6a8 CR3: 0660c000
CR4: 003606f0
Apr 11 07:43:36 kernel: DR0:  DR1: 
DR2: 
Apr 11 07:43:36 kernel: DR3:  DR6: fffe0ff0
DR7: 0400
Apr 11 07:43:36 kernel: Stack:
Apr 11 07:43:36 kernel:  0002 0201
c9000d6e3af8 c025ab06
Apr 11 07:43:36 kernel:  861be853 4111
880373ccfa00 8805250d0620
Apr 11 07:43:36 kernel:  8804fecc5050 0005
880448a4db88 0001
Apr 11 07:43:36 kernel: Call Trace:
Apr 11 07:43:36 kernel:  []
start_transaction+0x346/0x430 [btrfs]
Apr 11 07:43:36 kernel:  [] ? lookup_fast+0x53/0x350
Apr 11 07:43:36 kernel:  []
btrfs_start_transaction+0x22/0x30 [btrfs]
Apr 11 07:43:36 kernel:  [] btrfs_create+0x46/0x250 [btrfs]
Apr 11 07:43:36 kernel:  [] ? __inode_permission+0x3c/0xc0
Apr 11 07:43:36 kernel:  [] vfs_create+0xa5/0xe0
Apr 11 07:43:36 kernel:  [] path_openat+0x13c3/0x1400
Apr 11 07:43:36 kernel:  [] do_filp_open+0xb6/0x130
Apr 11 07:43:36 kernel:  [] do_sys_open+0x151/0x230
Apr 11 07:43:36 kernel:  [] SyS_open+0x28/0x40
Apr 11 07:43:36 kernel:  []
entry_SYSCALL_64_fastpath+0x12/0x86
Apr 11 07:43:36 kernel:  [] ?
entry_SYSCALL_64_fastpath+0x45/0x86
Apr 11 07:43:36 kernel:  [] ?
entry_SYSCALL_64_fastpath+0x45/0x86
Apr 11 07:43:36 kernel: Code: 44 21 e0 41 39 c4 75 32 49 63 f4 48 89
df e8 b5 cb ff ff 85 c0 78 18 f0 44 01 a3 fc 04 00 00 71 0a f0 44 29
a3 fc 04 00 00 cd 04  02 31 c0 5b 41 5c 5d 48 0f ba 2c 24 3f c3
A

Best Regards,
Tobias
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