lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Mon, 02 Aug 2010 14:57:56 +0900
From:	Akira Fujita <a-fujita@...jp.nec.com>
To:	Dmitry Monakhov <dmonakhov@...nvz.org>
CC:	akpm@...ux-foundation.org, adilger@...ger.ca,
	Jan Kara <jack@...e.cz>,
	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: BUG? ext3: Allocate blocks over quota limit with mmap

Hi Dmitry,

> It seems that private page_mkwrite will be sufficient.

Agree. This problem also breaks "reserved blocks count" semantics,
private page_mkwrite for ext2/3 will be necessary.
Thank you for working this on.

Regards,
Akira Fujita


(2010/08/02 14:22), Dmitry Monakhov wrote:
> Akira Fujita<a-fujita@...jp.nec.com>  writes:
> 
>> Hi ext3 maintainers,
>>
>> Could you look into this?
>> If this is not a problem, it is good though.
> Actually this is a problem. Because this issue makes quota just a fake
> limit. I've done this test for ext4 and was satisfied with result,
> but was too lazy to perform it on ext3/2 :(
> At least we have to have testcase for that in xfstest-qa.
> It seems that private page_mkwrite will be sufficient.
> I'm working on that.
>>
>> Regards,
>> Akira Fujita
>>
>>
>> (2010/07/29 11:08), Akira Fujita wrote:
>>> Hi,
>>>
>>> I found a problem that user can allocate blocks over quota limitation
>>> on ext3 (and ext2) with mmap.
>>> You can reproduce this with the following steps:
>>>
>>> 1. Enable user quota on ext3
>>>    [akira@...086 mnt]$ uname -r
>>>    2.6.35-rc6
>>>
>>>    [root@...086 mnt]# cat /proc/mounts  | grep  /dev/sda9
>>>    /dev/sda9 /mnt/mp1 ext3 rw,relatime,errors=continue,barrier=0,data=ordered,usrquota 0 0
>>>
>>>    [root@...086 mnt]# quotaon -p /mnt/mp1
>>>    group quota on /mnt/mp1 (/dev/sda9) is off
>>>    user quota on /mnt/mp1 (/dev/sda9) is on
>>>
>>>    [root@...086 mnt]# repquota -v /mnt/mp1
>>>    *** Report for user quotas on device /dev/sda9
>>>    Block grace time: 7days; Inode grace time: 7days
>>>                            Block limits                File limits
>>>    User            used    soft    hard  grace    used  soft  hard  grace
>>>    ----------------------------------------------------------------------
>>>    root      --    1229       0       0              4     0     0
>>>    akira     --       0     100    1000              0     0     0
>>>
>>>
>>> 2. Create sparse file on ext3
>>>    [akira@...086 mnt]$ df -T /mnt/mp1
>>>    Filesystem    Type   1K-blocks      Used Available Use% Mounted on
>>>    /dev/sda9     ext3       23300      1236     20861   6% /mnt/mp1
>>>
>>>    [akira@...086 mnt]$ dd if=/dev/zero of=/mnt/mp1/file bs=4096 seek=1MB count=1
>>>
>>> [akira@...086 mnt]$ ls -ls /mnt/mp1
>>>    total 26
>>>     7 -rw------- 1 root  root        7168 Jul 28 15:53 aquota.user
>>>     7 -rw-rw-r-- 1 akira akira 4096004096 Jul 28 15:53 file
>>>    12 drwx------ 2 root  root       12288 Jul 28 14:49 lost+found
>>>
>>>    [root@...086 mnt]# repquota -v /mnt/mp1
>>>    *** Report for user quotas on device /dev/sda9
>>>    Block grace time: 7days; Inode grace time: 7days
>>>                            Block limits                File limits
>>>    User            used    soft    hard  grace    used  soft  hard  grace
>>>    ----------------------------------------------------------------------
>>>    root      --    1228       0       0              3     0     0
>>>    akira     --       8     100    1000              2     0     0
>>>
>>> 3. Write data to "file" with mmap and msync.
>>>     (In this time, write size is 50MB. It's larger than partition size )
>>> 	e.g.
>>>           long long contents = 0x0002;
>>> 	fd = (file, O_APPEND | O_RDWR, 0666);
>>> 	p = mmap(NULL, psize, PROT_WRITE, MAP_SHARED, fd, offset);
>>> 	memset(p, contents++, psize);
>>> 	offset += psize
>>> 	munmap(p, psize);
>>> 	close(fd);
>>>
>>> 4. Then run out disk space, user uses all of the blocks.
>>>    [akira@...086 mnt]$ df -T /mnt/mp1
>>>    Filesystem    Type   1K-blocks      Used Available Use% Mounted on
>>>    /dev/sda9     ext3       23300     23300         0 100% /mnt/mp1
>>>                                       ~~~~~
>>>    [root@...086 mnt]# repquota -v /mnt/mp1
>>>    *** Report for user quotas on device /dev/sda9
>>>    Block grace time: 7days; Inode grace time: 7days
>>>                            Block limits                File limits
>>>    User            used    soft    hard  grace    used  soft  hard  grace
>>>    ----------------------------------------------------------------------
>>>    root      --    1228       0       0              3     0     0
>>>    akira     +-   22065     100    1000  6days       2     0     0
>>>                   ~~~~~
>>>
>>> memset() after mmap() triggers the pagefault and then __do_fault
>>> marks whole pages correspond to offset we specified as dirty.
>>> After 5 seconds (or call sync), the kjournald tries to write out all of dirtied pages
>>> with getting blocks to disk.
>>> kjournald has CAP_SYS_RESOURCE capability, therefore it can ignore
>>> quota limitation (also can use blocks for root user).
>>> As a result, user can have blocks over quota limitation,
>>> though quota is enabled.
>>> Note: ext4 has own page_mkwrite, so this problem does not happen on it.
>>>
>>> I guess behavior of kjournald is correct (write out all dirty pages of file),
>>> so we need some consideration for pagefault behavior for ext3 and ext2.
>>>
>>> Is this a bug?
>>>
>>> Regards,
>>> Akira Fujita
>>>
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
>>> the body of a message to majordomo@...r.kernel.org
>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
>> the body of a message to majordomo@...r.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

-- 
Akira Fujita <a-fujita@...jp.nec.com>

The First Fundamental Software Development Group,
Software Development Division,
NEC Software Tohoku, Ltd.

--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Powered by blists - more mailing lists