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Date:	Mon, 16 May 2011 12:11:54 +0200
From:	Jan Kara <jack@...e.cz>
To:	Amir Goldstein <amir73il@...il.com>
Cc:	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	Theodore Tso <tytso@....edu>, Jan Kara <jack@...e.cz>
Subject: Re: [PATCH] ext4: fix NULL pointer dereference in ext4_quota_off

On Mon 16-05-11 12:31:15, Amir Goldstein wrote:
> This fixes a bug in commit 21f97697 (ext4: remove unnecessary [cm]time
> update of quota file)
> 
> The above commit was merged for 2.6.39-rc3 and introduced a crash
> in xfstest 232 (Run fsstress with quotas enabled and verify accounted
> quotas in the end).
> 
> Signed-off-by: Amir Goldstein <amir73il@...rs.sf.net>
  Ah, I see we worked on the patch together :). Anyway, Ted can pick any of
them I guess.

								Honza
> ---
> 
> This fix solves the crash on my system, but the test still fails with the
> following output:
> 
> QA output created by 232
> 
> Testing fsstress
> 
> fsstress -n 2000 -d outdir -p 7
> seed = S
> Comparing user usage
> 3a4,493
> > #1        --    2456       0       0             13     0     0
> > #10       --       0       0       0              1     0     0
> > #10098    --     556       0       0              1     0     0
> > #1023     --      20       0       0              1     0     0
> > #10253    --       0       0       0              1     0     0
> > #1026286  --       4       0       0              1     0     0
> > #103086187 --       4       0       0              1     0     0
> > #1036     --       0       0       0              1     0     0
> > #1052282  --       4       0       0              1     0     0
> > #1057     --     260       0       0              1     0     0
> 
> I checked with kernel 2.6.38 and the test passes.
> I also tried reverting the commit, but the test still fails.
> 
> In any case, the fix resolved the following crash:
> 
> [ 1319.112544] EXT4-fs (sda8): mounted filesystem with ordered data
> mode. Opts: acl,user_xattr,usrquota,grpquota
> [ 1319.270023] EXT4-fs (sda8): re-mounted. Opts: (null)
> [ 1319.271464] EXT4-fs (sda8): re-mounted. Opts: (null)
> [ 1368.214854] BUG: unable to handle kernel NULL pointer dereference
> at 0000000000000018
> [ 1368.219348] IP: [<ffffffff8122e152>] ext4_quota_off+0x42/0xd0
> [ 1368.221628] PGD 0
> [ 1368.222978] Oops: 0000 [#2] SMP
> [ 1368.222978] last sysfs file:
> /sys/devices/system/cpu/cpu3/cache/index2/shared_cpu_map
> [ 1368.222978] CPU 0
> [ 1368.222978] Modules linked in: binfmt_misc parport_pc ppdev
> snd_hda_codec_realtek snd_hda_intel snd_hda_codec i915 snd_hwdep
> snd_pcm drm_kms_helper drm snd_seq_midi snd_rawmidi e1000e
> snd_seq_midi_event i2c_algo_bit snd_seq lp firewire_ohci firewire_core
> snd_timer snd_seq_device snd soundcore snd_page_alloc psmouse parport
> pata_marvell usbhid hid video intel_agp intel_gtt tpm_tis crc_itu_t
> serio_raw tpm tpm_bios
> [ 1368.222978]
> [ 1368.222978] Pid: 2691, comm: quotaon Tainted: G   M  D
> 2.6.39-rc7 #9                  /DQ35JO
> [ 1368.222978] RIP: 0010:[<ffffffff8122e152>]  [<ffffffff8122e152>]
> ext4_quota_off+0x42/0xd0
> [ 1368.222978] RSP: 0018:ffff8800c4bb3e28  EFLAGS: 00010292
> [ 1368.222978] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000018
> [ 1368.222978] RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000246
> [ 1368.222978] RBP: ffff8800c4bb3e48 R08: 0000000000000001 R09: 0000000000000000
> [ 1368.222978] R10: 0000000000000000 R11: 0000000000000000 R12: ffff880114576000
> [ 1368.222978] R13: ffff880114576000 R14: 0000000000000001 R15: 0000000000000000
> [ 1368.222978] FS:  00007f5c2bf97720(0000) GS:ffff88012bc00000(0000)
> knlGS:0000000000000000
> [ 1368.222978] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> [ 1368.222978] CR2: 0000000000000018 CR3: 00000000c693f000 CR4: 00000000000006f0
> [ 1368.222978] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [ 1368.222978] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> [ 1368.222978] Process quotaon (pid: 2691, threadinfo
> ffff8800c4bb2000, task ffff880116bc5ee0)
> [ 1368.222978] Stack:
> [ 1368.222978]  0000000000800003 0000000000000001 ffff880114576000
> 00000000ffffffda
> [ 1368.222978]  ffff8800c4bb3ef8 ffffffff811c9e05 0000000000000000
> 0000000000000000
> [ 1368.222978]  ffff8800c4bb3e78 ffff880114576068 ffff880115009800
> ffff880114576068
> [ 1368.222978] Call Trace:
> [ 1368.222978]  [<ffffffff811c9e05>] do_quotactl+0x4e5/0x560
> [ 1368.222978]  [<ffffffff815d376c>] ? down_read+0x4c/0x70
> [ 1368.222978]  [<ffffffff811711cf>] ? get_super+0x9f/0xd0
> [ 1368.222978]  [<ffffffff81189f78>] ? iput+0x48/0x200
> [ 1368.222978]  [<ffffffff811c9f4c>] sys_quotactl+0xcc/0x1a0
> [ 1368.222978]  [<ffffffff8116be26>] ? filp_close+0x66/0x90
> [ 1368.222978]  [<ffffffff812fd76e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
> [ 1368.222978]  [<ffffffff815dd2c2>] system_call_fastpath+0x16/0x1b
> [ 1368.222978] Code: 89 74 24 18 0f 1f 44 00 00 48 63 c6 49 89 fc 41
> 89 f6 48 8b 9c c7 60 03 00 00 48 8b 87 90 04 00 00 f6 40 73 08 0f 85
> 7e 00 00 00
> [ 1368.222978]  8b 7b 18 be 01 00 00 00 e8 c0 fb ff ff 48 3d 00 f0 ff ff 49
> [ 1368.222978] RIP  [<ffffffff8122e152>] ext4_quota_off+0x42/0xd0
> [ 1368.222978]  RSP <ffff8800c4bb3e28>
> [ 1368.222978] CR2: 0000000000000018
> [ 1368.310246] ---[ end trace 62a147f050ade229 ]---
> 
> 
>  fs/ext4/super.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index fc827bb..2689351 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -4681,6 +4681,9 @@ static int ext4_quota_off(struct super_block
> *sb, int type)
>  	if (test_opt(sb, DELALLOC))
>  		sync_filesystem(sb);
> 
> +	if (!inode)
> +		goto out;
> +
>  	/* Update modification times of quota files when userspace can
>  	 * start looking at them */
>  	handle = ext4_journal_start(inode, 1);
> -- 
> 1.7.4.1
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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