linux-kernel - Re: [Stable-review] [patch 31/38] ARM: 6891/1: prevent heap corruption in OABI semtimedop

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Date:	Mon, 9 May 2011 22:09:19 +0200 (CEST)
From:	Jesper Juhl <jj@...osbits.net>
To:	Ben Hutchings <ben@...adent.org.uk>
cc:	Dan Rosenberg <drosenberg@...curity.com>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Greg KH <gregkh@...e.de>, linux-kernel@...r.kernel.org,
	stable@...nel.org, akpm@...ux-foundation.org,
	torvalds@...ux-foundation.org, stable-review@...nel.org,
	alan@...rguk.ukuu.org.uk
Subject: Re: [Stable-review] [patch 31/38] ARM: 6891/1: prevent heap corruption
 in OABI semtimedop

On Sat, 7 May 2011, Ben Hutchings wrote:

> On Thu, 2011-05-05 at 17:11 -0700, Greg KH wrote:
> > 2.6.38-stable review patch.  If anyone has any objections, please let us know.
> > 
> > ------------------
> > 
> > From: Dan Rosenberg <drosenberg@...curity.com>
> > 
> > commit 0f22072ab50cac7983f9660d33974b45184da4f9 upstream.
> > 
> > When CONFIG_OABI_COMPAT is set, the wrapper for semtimedop does not
> > bound the nsops argument.  A sufficiently large value will cause an
> > integer overflow in allocation size, followed by copying too much data
> > into the allocated buffer.  Fix this by restricting nsops to SEMOPM.
> > Untested.
> > 
> > Signed-off-by: Dan Rosenberg <drosenberg@...curity.com>
> > Signed-off-by: Russell King <rmk+kernel@....linux.org.uk>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
> > 
> > ---
> >  arch/arm/kernel/sys_oabi-compat.c |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > --- a/arch/arm/kernel/sys_oabi-compat.c
> > +++ b/arch/arm/kernel/sys_oabi-compat.c
> > @@ -311,7 +311,7 @@ asmlinkage long sys_oabi_semtimedop(int
> >  	long err;
> >  	int i;
> >  
> > -	if (nsops < 1)
> > +	if (nsops < 1 || nsops > SEMOPM)
> >  		return -EINVAL;
> 
> It's not that important, but the manual page says the error code should
> E2BIG in the latter case.
> 

So something like this...

Return correct error (E2BIG) when nsops is greater than SEMOPM in 
sys_oabi_semtimedop. The man page (semtimedop(2)) lists this as the proper 
error in ths case: 
"E2BIG  The argument nsops is greater than SEMOPM, the maximum number of 
operations allowed per system call."

Signed-off-by: Jesper Juhl <jj@...osbits.net>
Reported-by: Ben Hutchings <ben@...adent.org.uk>
--
 sys_oabi-compat.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/arm/kernel/sys_oabi-compat.c b/arch/arm/kernel/sys_oabi-compat.c
index af0aaeb..c196ad7 100644
--- a/arch/arm/kernel/sys_oabi-compat.c
+++ b/arch/arm/kernel/sys_oabi-compat.c
@@ -311,8 +311,10 @@ asmlinkage long sys_oabi_semtimedop(int semid,
 	long err;
 	int i;
 
-	if (nsops < 1 || nsops > SEMOPM)
+	if (nsops < 1)
 		return -EINVAL;
+	else if (nsops > SEMOPM)
+		return -E2BIG;
 	sops = kmalloc(sizeof(*sops) * nsops, GFP_KERNEL);
 	if (!sops)
 		return -ENOMEM;



-- 
Jesper Juhl <jj@...osbits.net>       http://www.chaosbits.net/
Don't top-post http://www.catb.org/jargon/html/T/top-post.html
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