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Message-ID: <4C565E64.3070407@rs.jp.nec.com> 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
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