[PATCH for stable] kbuild: Fix modpost segfault

[PATCH for stable] kbuild: Fix modpost segfault

[Michal Marek]

Hi Greg,

please add this to stable, it's a bug that started showing up with newer
gcc. The upstream commit is 1c938663d58b5b2965976a6f54cc51b5d6f691aa.

Thanks,
Michal

From: Krzysztof Halasa <khc@pm.waw.pl>

Alan <alan@clueserver.org> writes:

> program: /home/alan/GitTrees/linux-2.6-mid-ref/scripts/mod/modpost -o
> Module.symvers -S vmlinux.o
>
> Program received signal SIGSEGV, Segmentation fault.

It just hit me.
It's the offset calculation in reloc_location() which overflows:
        return (void *)elf->hdr + sechdrs[section].sh_offset +
               (r->r_offset - sechdrs[section].sh_addr);

E.g. for the first rodata r entry:
r->r_offset < sechdrs[section].sh_addr
and the expression in the parenthesis produces 0xFFFFFFE0 or something
equally wise.

Reported-by: Alan <alan@clueserver.org>
Signed-off-by: Krzysztof Hałasa <khc@pm.waw.pl>
Tested-by: Alan <alan@clueserver.org>
Signed-off-by: Michal Marek <mmarek@suse.cz>


diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 3318692..f877900 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -1342,7 +1342,7 @@ static unsigned int *reloc_location(struct elf_info *elf,
 	int section = sechdr->sh_info;
 
 	return (void *)elf->hdr + sechdrs[section].sh_offset +
-		(r->r_offset - sechdrs[section].sh_addr);
+		r->r_offset - sechdrs[section].sh_addr;
 }
 
 static int addend_386_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r)

Re: [stable] [PATCH for stable] kbuild: Fix modpost segfault

[Greg KH]

On Tue, Jun 29, 2010 at 11:43:42AM +0200, Michal Marek wrote:
> Hi Greg,
> 
> please add this to stable, it's a bug that started showing up with newer
> gcc. The upstream commit is 1c938663d58b5b2965976a6f54cc51b5d6f691aa.

What -stable kernels do you want it applied to?  .27, .32, .33, and/or
.34?

thanks,

greg k-h

Re: [stable] [PATCH for stable] kbuild: Fix modpost segfault

[Michal Marek]

On 29.6.2010 14:54, Greg KH wrote:
> On Tue, Jun 29, 2010 at 11:43:42AM +0200, Michal Marek wrote:
>> Hi Greg,
>>
>> please add this to stable, it's a bug that started showing up with newer
>> gcc. The upstream commit is 1c938663d58b5b2965976a6f54cc51b5d6f691aa.
> 
> What -stable kernels do you want it applied to?  .27, .32, .33, and/or
> .34?

I'd say all of them. I just tried it and applies cleanly.

Michal

Re: [stable] [PATCH for stable] kbuild: Fix modpost segfault

[Greg KH]

On Tue, Jun 29, 2010 at 03:33:14PM +0200, Michal Marek wrote:
> On 29.6.2010 14:54, Greg KH wrote:
> > On Tue, Jun 29, 2010 at 11:43:42AM +0200, Michal Marek wrote:
> >> Hi Greg,
> >>
> >> please add this to stable, it's a bug that started showing up with newer
> >> gcc. The upstream commit is 1c938663d58b5b2965976a6f54cc51b5d6f691aa.
> > 
> > What -stable kernels do you want it applied to?  .27, .32, .33, and/or
> > .34?
> 
> I'd say all of them. I just tried it and applies cleanly.

Ok, thanks, will do.

greg k-h

Re: [stable] [PATCH for stable] kbuild: Fix modpost segfault

[Alan]

On Tue, 2010-06-29 at 06:39 -0700, Greg KH wrote: 
> On Tue, Jun 29, 2010 at 03:33:14PM +0200, Michal Marek wrote:
> > On 29.6.2010 14:54, Greg KH wrote:
> > > On Tue, Jun 29, 2010 at 11:43:42AM +0200, Michal Marek wrote:
> > >> Hi Greg,
> > >>
> > >> please add this to stable, it's a bug that started showing up with newer
> > >> gcc. The upstream commit is 1c938663d58b5b2965976a6f54cc51b5d6f691aa.
> > > 
> > > What -stable kernels do you want it applied to?  .27, .32, .33, and/or
> > > .34?
> > 
> > I'd say all of them. I just tried it and applies cleanly.
> 
> Ok, thanks, will do.

Thanks.  That fixes a major build problem for me.