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[PATCH v3 12/19] x86, kaslr: Fix a bug that relocation can not be handled when kernel is loaded above 2G

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  [PATCH v3 12/19] x86, kaslr: Fix a bug that relocation can not be handled when kernel is loaded above 2G Baoquan He <bhe@redhat.com> - 2016-03-04 17:30 +0100
    Re: [PATCH v3 12/19] x86, kaslr: Fix a bug that relocation can not be  handled when kernel is loaded above 2G Kees Cook <keescook@chromium.org> - 2016-03-08 00:40 +0100
      Re: [PATCH v3 12/19] x86, kaslr: Fix a bug that relocation can not  be handled when kernel is loaded above 2G Baoquan He <bhe@redhat.com> - 2016-03-08 06:30 +0100

#1350414 — [PATCH v3 12/19] x86, kaslr: Fix a bug that relocation can not be handled when kernel is loaded above 2G

When process 32 bit relocation tables a local variable 'extended'
is defined to calculate the physical address of relocs entry.
However its type is 'int' which is enough for i386, but not enough
for x86_64. That's why relocation can only be handled under 2G.
Otherwise a overflow will happen and cause system hang.

Here change it to 'long' as 32 bit inverse relocation processing
does, and this change is safe for i386 relocation handling.

Signed-off-by: Baoquan He <bhe@redhat.com>
---
 arch/x86/boot/compressed/misc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 4b2cd0c..70445c3 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -298,7 +298,7 @@ static void handle_relocations(void *output, unsigned long output_len)
 	 * So we work backwards from the end of the decompressed image.
 	 */
 	for (reloc = output + output_len - sizeof(*reloc); *reloc; reloc--) {
-		int extended = *reloc;
+		long extended = *reloc;
 		extended += map;
 
 		ptr = (unsigned long)extended;
-- 
2.5.0

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#1352221 — Re: [PATCH v3 12/19] x86, kaslr: Fix a bug that relocation can not be handled when kernel is loaded above 2G

On Fri, Mar 4, 2016 at 8:25 AM, Baoquan He <bhe@redhat.com> wrote:
> When process 32 bit relocation tables a local variable 'extended'
> is defined to calculate the physical address of relocs entry.
> However its type is 'int' which is enough for i386, but not enough
> for x86_64. That's why relocation can only be handled under 2G.
> Otherwise a overflow will happen and cause system hang.
>
> Here change it to 'long' as 32 bit inverse relocation processing
> does, and this change is safe for i386 relocation handling.
>
> Signed-off-by: Baoquan He <bhe@redhat.com>

Acked-by: Kees Cook <keescook@chromium.org>

This patch should probably be moved up into the start of this series
instead of living in the middle here, since it's a clear stand-alone
bug fix.

-Kees

> ---
>  arch/x86/boot/compressed/misc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
> index 4b2cd0c..70445c3 100644
> --- a/arch/x86/boot/compressed/misc.c
> +++ b/arch/x86/boot/compressed/misc.c
> @@ -298,7 +298,7 @@ static void handle_relocations(void *output, unsigned long output_len)
>          * So we work backwards from the end of the decompressed image.
>          */
>         for (reloc = output + output_len - sizeof(*reloc); *reloc; reloc--) {
> -               int extended = *reloc;
> +               long extended = *reloc;
>                 extended += map;
>
>                 ptr = (unsigned long)extended;
> --
> 2.5.0
>



-- 
Kees Cook
Chrome OS & Brillo Security

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#1352639 — Re: [PATCH v3 12/19] x86, kaslr: Fix a bug that relocation can not be handled when kernel is loaded above 2G

On 03/07/16 at 03:30pm, Kees Cook wrote:
> On Fri, Mar 4, 2016 at 8:25 AM, Baoquan He <bhe@redhat.com> wrote:
> > When process 32 bit relocation tables a local variable 'extended'
> > is defined to calculate the physical address of relocs entry.
> > However its type is 'int' which is enough for i386, but not enough
> > for x86_64. That's why relocation can only be handled under 2G.
> > Otherwise a overflow will happen and cause system hang.
> >
> > Here change it to 'long' as 32 bit inverse relocation processing
> > does, and this change is safe for i386 relocation handling.
> >
> > Signed-off-by: Baoquan He <bhe@redhat.com>
> 
> Acked-by: Kees Cook <keescook@chromium.org>
> 
> This patch should probably be moved up into the start of this series
> instead of living in the middle here, since it's a clear stand-alone
> bug fix.

Of course. Will put it in the start of this series. 

Thanks.

> 
> -Kees
> 
> > ---
> >  arch/x86/boot/compressed/misc.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
> > index 4b2cd0c..70445c3 100644
> > --- a/arch/x86/boot/compressed/misc.c
> > +++ b/arch/x86/boot/compressed/misc.c
> > @@ -298,7 +298,7 @@ static void handle_relocations(void *output, unsigned long output_len)
> >          * So we work backwards from the end of the decompressed image.
> >          */
> >         for (reloc = output + output_len - sizeof(*reloc); *reloc; reloc--) {
> > -               int extended = *reloc;
> > +               long extended = *reloc;
> >                 extended += map;
> >
> >                 ptr = (unsigned long)extended;
> > --
> > 2.5.0
> >
> 
> 
> 
> -- 
> Kees Cook
> Chrome OS & Brillo Security

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