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

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Date:   Mon, 1 Jan 2018 15:41:10 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Nicholas Mc Guire <der.herr@...r.at>
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()

2018-01-01 0:45 GMT+09:00 Nicholas Mc Guire <der.herr@...r.at>:
> 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).


Remove the comment line in
scripts/mod/empty.c







> 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
> --
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-- 
Best Regards
Masahiro Yamada