From: Jan Kara <jack@suse.cz>
To: Jeff Merkey <linux.mdb@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Theodore Ts'o <tytso@mit.edu>, Jan Kara <jack@suse.com>,
linux-ext4@vger.kernel.org
Subject: Re: [BUG REPORT] NULL pointer dereference in jdb2_journal_grab_journal_head (RDI)
Date: Mon, 25 Jan 2016 13:30:59 +0100 [thread overview]
Message-ID: <20160125123059.GB24938@quack.suse.cz> (raw)
In-Reply-To: <CAO6TR8Vhxjp-nX-wPXeBLOPmsHcb7_3y2uxk7x_V19o8hTZG0g@mail.gmail.com>
On Sat 23-01-16 09:42:52, Jeff Merkey wrote:
> If I leave the system in the debugger console overnight with all the
> processors suspended for about 8 hours, then type go, the following
> bug shows up during file I/O. This particular bug showed up while
> using git to update some branches.
>
> I have only seen this bug once and I attempted to reproduce it to get
> a trace dump but have not been able to trigger it again. The NULL
> pointer is RDI set to NULL while trying to obtain a lock.
>
> (2)> .z grab_journal
> ffffffffa00bb740 t jbd2_journal_grab_journal_head [jbd2]
> (2)> u ffffffffa00bb740
> jbd2|jbd2_journal_grab_journal_head:
> 0xffffffffa00bb740 0F1F440000 nop DWORD PTR [rax+rax]=0x0
> 0xffffffffa00bb745 55 push rbp
> 0xffffffffa00bb746 4889E5 mov rbp,rsp
> <<<<<<<<<<<< Crashes here with RDI set to NULL
> 0xffffffffa00bb749 F00FBA2F18 lock bts DWORD PTR [rdi]=0x0,0x18
> <<<<<<<<<<<<
Thanks for report. Ok, this means jbd2_journal_grab_journal_head() got
called with 'bh == NULL'. That is certainly wrong but unless we know a full
stack trace, it's hard to guess what went wrong.
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2016-01-25 12:30 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-23 16:42 [BUG REPORT] NULL pointer dereference in jdb2_journal_grab_journal_head (RDI) Jeff Merkey
2016-01-23 16:54 ` Jeff Merkey
2016-01-25 12:30 ` Jan Kara [this message]
2016-01-25 15:41 ` Jeff Merkey
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