Patchwork [v2] powerpc: fix personality handling in ppc64_personality()

login
register
mail settings
Submitter Jiri Kosina
Date Aug. 2, 2012, 7:10 a.m.
Message ID <alpine.LNX.2.00.1208020907490.14910@pobox.suse.cz>
Download mbox | patch
Permalink /patch/174684/
State Not Applicable
Delegated to: Benjamin Herrenschmidt
Headers show

Comments

Jiri Kosina - Aug. 2, 2012, 7:10 a.m.
Directly comparing current->personality against PER_LINUX32 doesn't work
in cases when any of the personality flags stored in the top three bytes
are used.

Directly forcefully setting personality to PER_LINUX32 or PER_LINUX
discards any flags stored in the top three bytes

Use personality() macro to compare only PER_MASK bytes and make sure that
we are setting only the bits that should be set, instead of
overwriting the whole value.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
---

changed since v1: fix the bit ops to reflect the fact that PER_LINUX is 
actually 0

 arch/powerpc/kernel/syscalls.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)
Benjamin Herrenschmidt - Sept. 5, 2012, 2:54 a.m.
On Thu, 2012-08-02 at 09:10 +0200, Jiri Kosina wrote:
> Directly comparing current->personality against PER_LINUX32 doesn't work
> in cases when any of the personality flags stored in the top three bytes
> are used.
> 
> Directly forcefully setting personality to PER_LINUX32 or PER_LINUX
> discards any flags stored in the top three bytes
> 
> Use personality() macro to compare only PER_MASK bytes and make sure that
> we are setting only the bits that should be set, instead of
> overwriting the whole value.
> 
> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
> ---
> 
> changed since v1: fix the bit ops to reflect the fact that PER_LINUX is 
> actually 0

Had already merged v1 (oops.. didn't spot the issue with PER_LINUX being
0). Can you send an incremental fixup ?

Cheers,
Ben.

>  arch/powerpc/kernel/syscalls.c |    8 ++++----
>  1 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/syscalls.c b/arch/powerpc/kernel/syscalls.c
> index f2496f2..dc1558e 100644
> --- a/arch/powerpc/kernel/syscalls.c
> +++ b/arch/powerpc/kernel/syscalls.c
> @@ -107,11 +107,11 @@ long ppc64_personality(unsigned long personality)
>  	long ret;
>  
>  	if (personality(current->personality) == PER_LINUX32
> -	    && personality == PER_LINUX)
> -		personality = PER_LINUX32;
> +	    && personality(personality) == PER_LINUX)
> +		personality |= PER_LINUX32;
>  	ret = sys_personality(personality);
> -	if (ret == PER_LINUX32)
> -		ret = PER_LINUX;
> +	if (personality(ret) == PER_LINUX32)
> +		ret &= ~PER_LINUX32;
>  	return ret;
>  }
>  #endif
> -- 
> 1.7.3.1
>
Jiri Kosina - Sept. 5, 2012, 8:56 a.m.
On Wed, 5 Sep 2012, Benjamin Herrenschmidt wrote:

> > Directly comparing current->personality against PER_LINUX32 doesn't work
> > in cases when any of the personality flags stored in the top three bytes
> > are used.
> > 
> > Directly forcefully setting personality to PER_LINUX32 or PER_LINUX
> > discards any flags stored in the top three bytes
> > 
> > Use personality() macro to compare only PER_MASK bytes and make sure that
> > we are setting only the bits that should be set, instead of
> > overwriting the whole value.
> > 
> > Signed-off-by: Jiri Kosina <jkosina@suse.cz>
> > ---
> > 
> > changed since v1: fix the bit ops to reflect the fact that PER_LINUX is 
> > actually 0
> 
> Had already merged v1 (oops.. didn't spot the issue with PER_LINUX being
> 0). Can you send an incremental fixup ?

Hi Benjamin,

actually commit 7256a5d2da56 seems to contain the correct PER_LINUX 
handling, so seems like you picked the right one :)

Thanks,
Benjamin Herrenschmidt - Sept. 5, 2012, 9:13 p.m.
On Wed, 2012-09-05 at 10:56 +0200, Jiri Kosina wrote:

> Hi Benjamin,
> 
> actually commit 7256a5d2da56 seems to contain the correct PER_LINUX 
> handling, so seems like you picked the right one :)
> 

Odd, they looked different around the use of PER_MASK when I looked but
I was tired & jet lagged, so I might have just had a brain fail...

Cheers,
Ben.
Jiri Kosina - Sept. 6, 2012, 8:46 a.m.
On Thu, 6 Sep 2012, Benjamin Herrenschmidt wrote:

> > actually commit 7256a5d2da56 seems to contain the correct PER_LINUX 
> > handling, so seems like you picked the right one :)
> > 
> 
> Odd, they looked different around the use of PER_MASK when I looked but

The original patch had

	personality &= ~PER_LINUX | PER_LINUX32;

Which is bogus, exactly because ~PER_LINUX is -1.

I then used

	personality = (personality & ~PER_MASK) | PER_LINUX32;

which is correct and perhaps a little bit more descriptive, and that is 
what you have merged, so all is fine.

> I was tired & jet lagged, so I might have just had a brain fail...

Probably just missed that the first patch used PER_LINUX and the second 
one PER_MASK, or whatever.

Anyway, thanks.

Patch

diff --git a/arch/powerpc/kernel/syscalls.c b/arch/powerpc/kernel/syscalls.c
index f2496f2..dc1558e 100644
--- a/arch/powerpc/kernel/syscalls.c
+++ b/arch/powerpc/kernel/syscalls.c
@@ -107,11 +107,11 @@  long ppc64_personality(unsigned long personality)
 	long ret;
 
 	if (personality(current->personality) == PER_LINUX32
-	    && personality == PER_LINUX)
-		personality = PER_LINUX32;
+	    && personality(personality) == PER_LINUX)
+		personality |= PER_LINUX32;
 	ret = sys_personality(personality);
-	if (ret == PER_LINUX32)
-		ret = PER_LINUX;
+	if (personality(ret) == PER_LINUX32)
+		ret &= ~PER_LINUX32;
 	return ret;
 }
 #endif