From: Amon Ott <a.ott@m-privacy.de>
To: "Yan, Zheng" <zyan@redhat.com>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
ceph-devel@vger.kernel.org, linux-ext4@vger.kernel.org
Cc: akpm@linux-foundation.org, viro@zeniv.linux.org.uk, jlayton@redhat.com
Subject: Re: [PATCH] mm: save current->journal_info before calling fault/page_mkwrite
Date: Wed, 13 Dec 2017 14:53:55 +0100 [thread overview]
Message-ID: <17a0b877-fa5e-fb1d-aa6d-2390d792c6e6@m-privacy.de> (raw)
In-Reply-To: <20171213035836.916-1-zyan@redhat.com>
Am 13.12.2017 um 04:58 schrieb Yan, Zheng:
> We recently got an Oops report:
>
> BUG: unable to handle kernel NULL pointer dereference at (null)
> IP: jbd2__journal_start+0x38/0x1a2
> [...]
> Call Trace:
> ext4_page_mkwrite+0x307/0x52b
> _ext4_get_block+0xd8/0xd8
> do_page_mkwrite+0x6e/0xd8
> handle_mm_fault+0x686/0xf9b
> mntput_no_expire+0x1f/0x21e
> __do_page_fault+0x21d/0x465
> dput+0x4a/0x2f7
> page_fault+0x22/0x30
> copy_user_generic_string+0x2c/0x40
> copy_page_to_iter+0x8c/0x2b8
> generic_file_read_iter+0x26e/0x845
> timerqueue_del+0x31/0x90
> ceph_read_iter+0x697/0xa33 [ceph]
> hrtimer_cancel+0x23/0x41
> futex_wait+0x1c8/0x24d
> get_futex_key+0x32c/0x39a
> __vfs_read+0xe0/0x130
> vfs_read.part.1+0x6c/0x123
> handle_mm_fault+0x831/0xf9b
> __fget+0x7e/0xbf
> SyS_read+0x4d/0xb5
>
> The reason is that page fault can happen when one filesystem copies
> data from/to userspace, the filesystem may set current->journal_info.
> If the userspace memory is mapped to a file on another filesystem,
> the later filesystem may also want to use current->journal_info.
>
> Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Reported-and-tested-by: Amon Ott <a.ott@m-privacy.de>
Thanks a lot for the patch! I have ported your patch to 4.9.68, tested
and the bug seems fixed now.
Amon Ott
--
Dr. Amon Ott
m-privacy GmbH Tel: +49 30 24342334
Werner-Voß-Damm 62 Fax: +49 30 99296856
12101 Berlin http://www.m-privacy.de
Amtsgericht Charlottenburg, HRB 84946
Geschäftsführer:
Dipl.-Kfm. Holger Maczkowsky,
Roman Maczkowsky
GnuPG-Key-ID: 0x2DD3A649
next prev parent reply other threads:[~2017-12-13 14:04 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-13 3:58 [PATCH] mm: save current->journal_info before calling fault/page_mkwrite Yan, Zheng
2017-12-13 13:53 ` Amon Ott [this message]
2017-12-14 0:59 ` Andrew Morton
2017-12-14 0:59 ` Andrew Morton
2017-12-14 2:09 ` Yan, Zheng
2017-12-14 2:09 ` Yan, Zheng
2017-12-14 2:18 ` Andrew Morton
2017-12-14 2:18 ` Andrew Morton
2017-12-14 2:20 ` Yan, Zheng
2017-12-14 2:20 ` Yan, Zheng
2017-12-14 2:30 ` Andrew Morton
2017-12-14 2:30 ` Andrew Morton
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