linux-kernel - Re: [PATCH v2] fixdep: exit with error code in error branches of do_config

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Date:   Sun, 31 Dec 2017 15:45:48 +0000
From:   Nicholas Mc Guire <der.herr@...r.at>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Lukas Bulwahn <lukas.bulwahn@...il.com>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        sil2review@...ts.osadl.org, Michal Marek <michal.lkml@...kovi.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] fixdep: exit with error code in error branches of
 do_config_file()

On Sun, Dec 31, 2017 at 01:51:33AM +0900, Masahiro Yamada wrote:
> 2017-12-22 4:10 GMT+09:00 Lukas Bulwahn <lukas.bulwahn@...il.com>:
> > do_config_file() should exit with an error code, and not return if it fails
> > as then the error in do_config_file() would go unnoticed in the current
> > code and allow the build to continue. The exit with error code will make
> > the build fail in those very exceptional cases. If this occurs, this
> > actually indicates a deeper problem in the execution of the kernel build
> > process.
> >
> > Now, that the function exists, we do not explicitly free memory and close
> > the file handlers in do_config_file(), as this is covered by exit().
> >
> > This issue in the fixdep script was introduced with its initial
> > implementation back in 2002 by the original author Kai Germaschewski with
> > this commit 04bd72170653 ("kbuild: Make dependencies at compile time").
> 
> "04bd72170653" is just confusing.
> 
> If you really want to mention this hash,
> please clearly say it is in the history repository
> outside of this.
> 
> 
> > This issue was identified during the review of a previous patch that
> > intended to address a memory leak detected by a static analysis tool.
> >
> > Link: https://lkml.org/lkml/2017/12/14/736
> >
> > Fixes: 04bd72170653 ("kbuild: Make dependencies at compile time")
> 
> Please drop this pointless Fixes tag
> because that commit is not reachable from this patch.
> 
> 
> 
> > Suggested-by: Nicholas Mc Guire <der.herr@...r.at>
> > Suggested-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> > Signed-off-by: Lukas Bulwahn <lukas.bulwahn@...il.com>
> > ---
> > compile tested on top of next-20171220 with clang and gcc
> > Change in v2:
> >   - no code change; only include proper Fixes tag and explain it
> >
> >  scripts/basic/fixdep.c | 11 +++++------
> >  1 file changed, 5 insertions(+), 6 deletions(-)
> >
> > diff --git a/scripts/basic/fixdep.c b/scripts/basic/fixdep.c
> > index bbf62cb..4274610 100644
> > --- a/scripts/basic/fixdep.c
> > +++ b/scripts/basic/fixdep.c
> > @@ -284,19 +284,18 @@ static void do_config_file(const char *filename)
> >                 exit(2);
> >         }
> >         if (st.st_size == 0) {
> > -               close(fd);
> > -               return;
> > +               fprintf(stderr, "fixdep: error empty file config file: ");
> > +               perror(filename);
> > +               exit(2);
> >         }
> 
> No.  This is correct as-is.
> 
> do_config_file() does not parse .cmd files
> but parse source files (.c .h .S etc.)
> 

What case for a legitimately empty source file would there be ?
the files being checked are assumed to be mandatory for the
given configuration right ? if so how can a configuration depend
on an empty file ? would that not point to a config problem and
rather be fixed there ? or am I misunderstanding this here ?

> Having an empty source file is rare, but possible.
>

putting a printf in the empty case handling and running a set of
randconfigs did not reveal such an event (10 runs). 

thx!
hofrat
 
> 
> 
> 
> 
> 
> >         map = malloc(st.st_size + 1);
> >         if (!map) {
> >                 perror("fixdep: malloc");
> > -               close(fd);
> > -               return;
> > +               exit(2);
> >         }
> >         if (read(fd, map, st.st_size) != st.st_size) {
> >                 perror("fixdep: read");
> > -               close(fd);
> > -               return;
> > +               exit(2);
> >         }
> >         map[st.st_size] = '\0';
> >         close(fd);
> > --
> > 2.7.4
> >
> 
> These two changes are OK.
> 
> 
> 
> -- 
> Best Regards
> Masahiro Yamada