Re: [SIL2review] [PATCH] fixdep: free memory on second error path of do_config_file

[Lukas Bulwahn]

On Mon, 18 Dec 2017, Masahiro Yamada wrote:

> 2017-12-15 17:23 GMT+09:00 Nicholas Mc Guire <der.herr@xxxxxxx>:
> > On Thu, Dec 14, 2017 at 08:54:10PM +0100, Lukas Bulwahn wrote:
> > > Commit dee81e988674 ("fixdep: faster CONFIG_ search") introduces the memory
> > > leak when `map = mmap(...)` was replaced with `map = malloc(...)` and
> > > `read(fd, map, ...)`. It introduces a new second error path, which does not
> > > free the allocated memory for `map`. We now correct that behavior and free
> > > `map` before the do_config_file() function returns.
> > >
> > > Facebook's static analysis tool Infer (http://fbinfer.com) found this
> > > memory leak:
> > >
> > >   scripts/basic/fixdep.c:297: error: MEMORY_LEAK
> > >     memory dynamically allocated by call to `malloc()` at line 290, \
> > >     column 8 is not reachable after line 297, column 3.
> > >
> > > Fixes: dee81e988674 ("fixdep: faster CONFIG_ search")
> > >
> > > Signed-off-by: Lukas Bulwahn <lukas.bulwahn@xxxxxxxxx>
> > Reviewed-by: Nicholas Mc Guire <der.herr@xxxxxxx>
> >
> > > ---
> > >  scripts/basic/fixdep.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > >
> > > diff --git a/scripts/basic/fixdep.c b/scripts/basic/fixdep.c
> > > index bbf62cb..131c450 100644
> > > --- a/scripts/basic/fixdep.c
> > > +++ b/scripts/basic/fixdep.c
> > > @@ -296,6 +296,7 @@ static void do_config_file(const char *filename)
> > >       if (read(fd, map, st.st_size) != st.st_size) {
> > >               perror("fixdep: read");
> > >               close(fd);
> > > +             free(map);
> >
> >  This looks reasonable but actually it is not clear why do_config_file()
> > should return at all if read fails as the read error would go unnoticed
> > in the current code and allow the build to continue. so this probably
> > should be an exit(2) here and not a return which would then take care
> > of the free() anyway.
>
> I agree.
>
> This should be exit(2).
>
> You can also remove close() as well since
> the operation system will close it anyway.
>
>
>
> >  Atleast I do not see the rational to allow continuation if the read
> > failed as the file should not be empty nor a mismatch with st.st_size
> > expected. If it were due to a EINTR then it still should terminate as
> > EINTR was not handled and we thus could miss a valid dependency.
> >
> >  Note: this probably also should be applied to the if (!map) condition
> > before as well, as at that point it is known that map > 0 and a malloc()
> > failure would allow skipping parse_config_file() for a valid config.
>
> I agree.  We should change this too.

I created a new patch with your requested changes, but I did not consider 
it a second version of this patch by the time of writing. You can find the 
new patch at:

v1: https://patchwork.kernel.org/patch/10126547/
v2: https://patchwork.kernel.org/patch/10128297/

This patch here is now superseded by the new patch. So, this patch here 
can be abandoned.

Lukas