Re: file access causes a kernel bug

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On 01/29/2014 04:39 PM, Richard Yao wrote:
> Gentoo systems have custom kernels made by their users. I can run through Matthew’s kernel config with him to make sure that all of the right options are checked this evening. If any changes are necessary, he can recompile.
> 
> On Jan 29, 2014, at 5:35 PM, Brian Behlendorf <behlendorf1@xxxxxxxx> wrote:
> 
>> On 01/29/14 13:36, Stephen Smalley wrote:
>>> On 01/29/2014 11:58 AM, Matthew Thode wrote:
>>>> On 01/29/2014 08:17 AM, Stephen Smalley wrote:
>>>>> On 01/29/2014 09:07 AM, Stephen Smalley wrote:
>>>>>> On 01/29/2014 08:55 AM, Paul Moore wrote:
>>>>>>> On Wednesday, January 29, 2014 02:11:45 AM Matthew Thode wrote:
>>>>>>>> On 01/29/2014 02:04 AM, Matthew Thode wrote:
>>>>>>>>> This happens consistantly, just ls a particular dir and wheeeeee.
>>>>>>>>>
>>>>>>>>> [  473.893141] ------------[ cut here ]------------
>>>>>>>>> [  473.962110] kernel BUG at security/selinux/ss/services.c:654!
>>>>>>>>> [  473.995314] invalid opcode: 0000 [#6] SMP
>>>>>>>>> [  474.027196] Modules linked in:
>>>>>>>>> [  474.058118] CPU: 0 PID: 8138 Comm: ls Tainted: G      D   I
>>>>>>>>> 3.13.0-grsec #1
>>>>>>>>> [  474.116637] Hardware name: Supermicro X8ST3/X8ST3, BIOS 2.0
>>>>>>>>> 07/29/10
>>>>>>>>> [  474.149768] task: ffff8805f50cd010 ti: ffff8805f50cd488 task.ti:
>>>>>>>>> ffff8805f50cd488
>>>>>>>>> [  474.183707] RIP: 0010:[<ffffffff814681c7>]  [<ffffffff814681c7>]
>>>>>>>>> context_struct_compute_av+0xce/0x308
>>>>>>>>> [  474.219954] RSP: 0018:ffff8805c0ac3c38  EFLAGS: 00010246
>>>>>>>>> [  474.252253] RAX: 0000000000000000 RBX: ffff8805c0ac3d94 RCX:
>>>>>>>>> 0000000000000100
>>>>>>>>> [  474.287018] RDX: ffff8805e8aac000 RSI: 00000000ffffffff RDI:
>>>>>>>>> ffff8805e8aaa000
>>>>>>>>> [  474.321199] RBP: ffff8805c0ac3cb8 R08: 0000000000000010 R09:
>>>>>>>>> 0000000000000006
>>>>>>>>> [  474.357446] R10: 0000000000000000 R11: ffff8805c567a000 R12:
>>>>>>>>> 0000000000000006
>>>>>>>>> [  474.419191] R13: ffff8805c2b74e88 R14: 00000000000001da R15:
>>>>>>>>> 0000000000000000
>>>>>>>>> [  474.453816] FS:  00007f2e75220800(0000) GS:ffff88061fc00000(0000)
>>>>>>>>> knlGS:0000000000000000
>>>>>>>>> [  474.489254] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>>>>>> [  474.522215] CR2: 00007f2e74716090 CR3: 00000005c085e000 CR4:
>>>>>>>>> 00000000000207f0
>>>>>>>>> [  474.556058] Stack:
>>>>>>>>> [  474.584325]  ffff8805c0ac3c98 ffffffff811b549b ffff8805c0ac3c98
>>>>>>>>> ffff8805f1190a40
>>>>>>>>> [  474.618913]  ffff8805a6202f08 ffff8805c2b74e88 00068800d0464990
>>>>>>>>> ffff8805e8aac860
>>>>>>>>> [  474.653955]  ffff8805c0ac3cb8 000700068113833a ffff880606c75060
>>>>>>>>> ffff8805c0ac3d94
>>>>>>>>> [  474.690461] Call Trace:
>>>>>>>>> [  474.723779]  [<ffffffff811b549b>] ? lookup_fast+0x1cd/0x22a
>>>>>>>>> [  474.778049]  [<ffffffff81468824>] security_compute_av+0xf4/0x20b
>>>>>>>>> [  474.811398]  [<ffffffff8196f419>] avc_compute_av+0x2a/0x179
>>>>>>>>> [  474.843813]  [<ffffffff8145727b>] avc_has_perm+0x45/0xf4
>>>>>>>>> [  474.875694]  [<ffffffff81457d0e>] inode_has_perm+0x2a/0x31
>>>>>>>>> [  474.907370]  [<ffffffff81457e76>] selinux_inode_getattr+0x3c/0x3e
>>>>>>>>> [  474.938726]  [<ffffffff81455cf6>] security_inode_getattr+0x1b/0x22
>>>>>>>>> [  474.970036]  [<ffffffff811b057d>] vfs_getattr+0x19/0x2d
>>>>>>>>> [  475.000618]  [<ffffffff811b05e5>] vfs_fstatat+0x54/0x91
>>>>>>>>> [  475.030402]  [<ffffffff811b063b>] vfs_lstat+0x19/0x1b
>>>>>>>>> [  475.061097]  [<ffffffff811b077e>] SyS_newlstat+0x15/0x30
>>>>>>>>> [  475.094595]  [<ffffffff8113c5c1>] ? __audit_syscall_entry+0xa1/0xc3
>>>>>>>>> [  475.148405]  [<ffffffff8197791e>] system_call_fastpath+0x16/0x1b
>>>>>>>>> [  475.179201] Code: 00 48 85 c0 48 89 45 b8 75 02 0f 0b 48 8b 45 a0 48
>>>>>>>>> 8b 3d 45 d0 b6 00 8b 40 08 89 c6 ff ce e8 d1 b0 06 00 48 85 c0 49 89 c7
>>>>>>>>> 75 02 <0f> 0b 48 8b 45 b8 4c 8b 28 eb 1e 49 8d 7d 08 be 80 01 00 00 e8
>>>>>>>>> [  475.255884] RIP  [<ffffffff814681c7>]
>>>>>>>>> context_struct_compute_av+0xce/0x308
>>>>>>>>> [  475.296120]  RSP <ffff8805c0ac3c38>
>>>>>>>>> [  475.328734] ---[ end trace f076482e9d754adc ]---
>>>>>>>>>
>>>>>>>>
>>>>>>>> sorry, forgot to add, this is for 3.13.0 as well.
>>>>>>>>
>>>>>>>> ls ./.config/ipython/profile_default/
>>>>>>>> Segmentation fault
>>>>>>>
>>>>>>> Thanks for passing this along, but can you elaborate a bit more on this?
>>>>>>> Distribution?  Kernel package?  SELinux policy?  Any unusual configuration?
>>>>>>> etc.
>>>>>>>
>>>>>>> I ask because I'm not seeing this problem on my system and it seems like a
>>>>>>> fairly basic thing to be broken; if there was an issue with 'ls' on 3.13 I
>>>>>>> expect we would be flooded with angry users right now ...
>>>>>>
>>>>>> Does it happen on any filesystem other than ZFS?
>>>>>>
>>>>>> Do you have any prior SELinux output leading up to this bug?
>>>>>
>>>>> Also, what policy are you using and what is the security context on that
>>>>> file?
>>>>>
>>>> Ok, one at a time :D
>>>>
>>>> I'm on gentoo using the strict policy (in permissive for now...)
>>>>
>>>> Kernel is 3.13 (zfs is built from git head as of 2014-01-26 (selinux
>>>> patches went in :D))
>>>>
>>>> using basepol 2.20130424
>>>>
>>>> No unusual config that I can think of.  I've found multiple files that
>>>> this happens with).
>>>>
>>>> Only on zfs that I can see
>>>>
>>>> Dunno what you mean by prior selinux output, just some random selinux
>>>> denials because restorecon -RF fails because of this.
>>>>
>>>> I can't see either the file name or the context of that file.  As soon
>>>> as anything tries to access anything about the file I get that backtrace.
>>>
>>> Looking at the code in question, I don't see any way to reach that BUG
>>> without memory corruption in the kernel.  Which could just as easily be
>>> in ZFS as anything else...
>>
>> Memory corruption is possible but we haven't seen any other evidence of that in ZFS.  If Gentoo has a kernel-debug package similar to Fedora/RHELs that may be worth a try.  The additional debugging may catch something non-obvious.
>>
>> Thanks,
>> Brian
> 
Ok, booted up without selinux, does this seem right to you (note the
empty security.selinux field for
'.config/ipython/profile_default/history.sqlite-journal').

# getfattr -n security.selinux .config/ipython/profile_default/*

# file: .config/ipython/profile_default/db
security.selinux="root:object_r:xdg_config_home_t"

# file: .config/ipython/profile_default/history.sqlite
security.selinux="root:object_r:xdg_config_home_t"

# file: .config/ipython/profile_default/history.sqlite-journal
security.selinux

# file: .config/ipython/profile_default/log
security.selinux="root:object_r:xdg_config_home_t"

# file: .config/ipython/profile_default/pid
security.selinux="root:object_r:xdg_config_home_t"

# file: .config/ipython/profile_default/security
security.selinux="root:object_r:xdg_config_home_t"

# file: .config/ipython/profile_default/startup
security.selinux="root:object_r:xdg_config_home_t"

storage ~ # touch asdasdasdadasdasd
storage ~ # getfattr -n security.selinux asdasdasdadasdasd
asdasdasdadasdasd: security.selinux: No such attribute



-- 
-- Matthew Thode

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