Re: [patch] kexec: potetially using uninitialized variable

Minfei Huang
2016-03-11T15:38:19Z

On 03/11/16 at 10:47am, walter harms wrote:
>
>
> Am 11.03.2016 10:19, schrieb Dan Carpenter:
> > On Fri, Mar 11, 2016 at 04:52:43PM +0800, Xunlei Pang wrote:
> >> Hi Dan,
> >>
> >> On 2016/03/11 at 16:07, Dan Carpenter wrote:
> >>> At the end of the function we check if "ret" has a negative error code,
> >>> but it seems possible that it is uninitialized.
> >>>
> >>> Fixes: 12db5562e035 ('kexec: load and relocate purgatory at kernel load time')
> >>> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> >>>
> >>> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> >>> index 503bc2d..63d1af3 100644
> >>> --- a/kernel/kexec_file.c
> >>> +++ b/kernel/kexec_file.c
> >>> @@ -795,7 +795,7 @@ out:
> >>>
> >>> static int kexec_apply_relocations(struct kimage *image)
> >>> {
> >>> - int i, ret;
> >>> + int i, ret = 0;
> >>> struct purgatory_info *pi = &image->purgatory_info;
> >>> Elf_Shdr *sechdrs = pi->sechdrs;
> >>>
> >>
> >> Look further, there is a condition at the beginning of the for loop:
> >>
> >>
> >> if (sechdrs[i].sh_type != SHT_RELA &&
> >> sechdrs[i].sh_type != SHT_REL)
> >> continue;
> >>
> >> So, I think that's ok, but I don't konw if GCC is smart enough not to throw warnings.
> >
> > Ah, right...
> >
> > This wasn't a GCC warning. GCC misses a lot of uninitialized variable
> > bugs so I'm doing this with Smatch.
> >
> > Anyway, I'll patch this up in Smatch to not warn about this.
> >
>
> I am not so sure about this. the point should be that the reviewer can read it easily
> not if gcc complains or not.

Hi, All.

I think we can modify the logic a bit to make code simple. Thus gcc will
not complain about any more, and the logic is earier.

Following is a draft patch.

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 007b791..7144e3b 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -887,7 +887,7 @@ static int kexec_apply_relocations(struct kimage *image)
if (sechdrs[i].sh_type = SHT_RELA)
ret = arch_kexec_apply_relocations_add(pi->ehdr,
sechdrs, i);
- else if (sechdrs[i].sh_type = SHT_REL)
+ else
ret = arch_kexec_apply_relocations(pi->ehdr,
sechdrs, i);
if (ret)

>
> just my 2 cents,
>
> re,
> wh
>
>