Re: [clear_page] 0ad07c8104 BUG: unable to handle kernel NULL pointer dereference at 0000000000000040

From: Fengguang Wu
Date: Sat Feb 18 2017 - 18:31:31 EST

Hi Borislav,

On Sat, Feb 18, 2017 at 03:48:00PM +0100, Borislav Petkov wrote:

please fix the 0day bot reporting. See below for more info.

On Sat, Feb 18, 2017 at 01:01:53PM +0800, Fengguang Wu wrote:

0day kernel testing robot got the below dmesg and the first bad commit is Borislav-Petkov/x86-Optimize-clear_page/20170210-053052

Can you make this point to the actual commit on github?

Your tree there has currently 47K branches and navigating through the
web interface takes forever.

Good point! I noticed it too while sending out the report. It'll be
showed as this in future:

commit 0ad07c8104eb5c12dfcb86581c1cc657183496cc
Author: Borislav Petkov <bp@xxxxxxx>
AuthorDate: Thu Feb 9 20:51:25 2017 +0100
Commit: 0day robot <fengguang.wu@xxxxxxxxx>
CommitDate: Fri Feb 10 05:30:58 2017 +0800

x86: Optimize clear_page()

Currently, we CALL clear_page() which then JMPs to the proper function
chosen by the alternatives.

What we should do instead is CALL the proper function directly. (This
was something Ingo suggested a while ago). So let's do that.

Measuring our favourite kernel build workload shows that there are no
significant changes in performance.


Signed-off-by: Borislav Petkov <bp@xxxxxxx>

Then, this is an old patch. You already sent me a bug report, I replied
with a fix but you didn't test the fix. Instead you're sending the same
old report.

Sorry the 2nd report was send out manually and I only checked the
emails in my _current_ mbox. Since the previous report email has been
archived, it slipped through the duplication check.

Here's the fix:

And the upstream submission of the new version:

Please fix the bot to pay attention to replies. If there is a special
way I should reply with a fix so that the bot retests with the same
config, please let me know.

CC Xiaolong. It's possible to automate the test-of-fixup-patches.
Firstly find out the original email report by the Message-ID being
replied to. Then fetch all the information required for deciding where
the patch should be applied to, parameters to auto-testing the patch.

In general, I think it would be a very cool idea to be able to reply to
the bot and say, "Dear bot, can you test this fix ontop with the exact
same guest, vm, kernel .config etc.

That would be lovely.

Yeah we have a TODO to do email based on-demand service, which looks
close to your proposal.

Thanks and keep up the good work!