Re: [PATCH v3] livepatch: Prevent to apply the patch once coming module notifier fails

Minfei Huang
2015-05-19T03:57:15Z

On 05/18/15 at 05:35pm, Petr Mladek wrote:
> On Mon 2015-05-18 21:00:57, Minfei Huang wrote:
> > On 05/18/15 at 02:08pm, Petr Mladek wrote:
> > > On Wed 2015-05-13 09:14:15, Josh Poimboeuf wrote:
...[snip]...
> > > > The patch isn't necessarily dead, since it might also include previously
> > > > enabled changes for vmlinux or other modules. It can actually be a
> > > > dangerous condition if there's a mismatch between old code in the module
> > > > and new code elsewhere. How about something like:
> > > >
> > > > "patch '%s' is in an inconsistent state!\n"
> > >
> > > It must not be dangerous, otherwise the patch could not get applied
> > > immediately.
> >
> > But kernel is in dangerous situation that the patch may corrupt it
> > later. So it is appropriate to notify the user.
>
> How exactly could the patch corrupt the system? Could you please give
> an example?
>

Please review the commit log where I show the step by step in thread.

> > >
> > > I would omit this message completely. It would just duplicate the
> > > warning printed by klp_module_notify_coming().
> > >
> >
> > This error message aims to tell this fact that this patch is in an
> > inconsistent state. If someone do not notify this error, it is fine,
> > because the inconsistent patch does not have change to be applied to the
> > kernel.
>
> But there is already printed a warning from
> klp_module_notify_coming(). I wonder why we need one more here.
>

Since the error messages are different for the different called function
in klp_module_notify_coming. It only shows that there is something wrong
to call the function.

It is prefer that livepatch can notify the user how the patch is, if
klp_module_notify_coming fails.

> > >
> > > > Also, there's no need to split up the string literal into two lines.
> > > > It's ok for a line to have more than 80 columns in that case.
> > >
> > > I suggest to run ./scripts/chechpatch.pl before you send any patch.
> > > It would catch the indentation problems, split of the string, ...
> >
> > I have used the script checkpatch.pl to verify the patch. And it passed
> > for the checking. About the indentation problems, it may be caused by
> > the sepcified vimrc file.
>
> I get the following warning on your patch:
>
> --- cut ---
> $> ./scripts/checkpatch.pl /prace/klp-module-notify-error-v3-iter1.patch
> WARNING: quoted string split across lines
> #181: FILE: kernel/livepatch/core.c:965:
> + pr_warn("patch '%s' is dead, remove it "
> + "or re-install the module '%s'\n",
>
> total: 0 errors, 1 warnings, 62 lines checked
>
> /prace/klp-module-notify-error-v3-iter1.patch has style problems, please review.
>
> If any of these errors are false positives, please report
> them to the maintainer, see CHECKPATCH in MAINTAINERS.
> --- cut ---

Yes. The error message is too long, then it across the lines.

>
> BTW: I do not see the problems with indentation.

Someone likes to use 4 blanks to instead of a tab. So the code may show
differently between them.

Thanks
Minfei

>
> Best Regards,
> Petr