Re: [PATCH V2] xfs: zero proper structure size for geometry calls

From: Jeffrey Hundstad <jeffrey.hundstad@mnsu.edu>
To: Dan Rosenberg <drosenberg@vsecurity.com>
Cc: Eric Sandeen <sandeen@sandeen.net>,
	Eugene Teo <eugeneteo@kernel.org>,
	xfs@oss.sgi.com
Subject: Re: [PATCH V2] xfs: zero proper structure size for geometry calls
Date: Tue, 01 Mar 2011 09:36:44 -0600	[thread overview]
Message-ID: <4D6D128C.6010503@mnsu.edu> (raw)
In-Reply-To: <1298984132.32568.3.camel@dan>

On 03/01/2011 06:55 AM, Dan Rosenberg wrote:
> On Tue, 2011-03-01 at 00:59 -0600, Eric Sandeen wrote:
>    
>> commit 493f3358cb289ccf716c5a14fa5bb52ab75943e5 added:
>>
>> +       memset(geo, 0, sizeof(*geo));
>>
>> but unfortunately we're dealing with a cast pointer here, and
>> the caller may actually have a smaller structure on the stack.
>> Zeroing out more leads to stack corruption traps:
>>
>> Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: f87aca93
>>
>> Pid: 262, comm: xfs_fsr Not tainted 2.6.38-rc6-493f3358cb2+ #1
>> Call Trace:
>>
>> [<c12991ac>] ? panic+0x50/0x150
>> [<c102ed71>] ? __stack_chk_fail+0x10/0x18
>> [<f87aca93>] ? xfs_ioc_fsgeometry_v1+0x56/0x5d [xfs]
>>
>> Fix this by zeroing out the structure in the callers, where we know
>> the actual size.
>>      
> Thanks for catching this early, and sorry for the misstep.
>
> Reviewed-by: Dan Rosenberg<drosenberg@vsecurity.com>
>
>    
>> Reported-by: Jeffrey Hundstad<jeffrey.hundstad@mnsu.edu>
>> Signed-off-by: Eric Sandeen<sandeen@redhat.com>
>> ---
>>
>> V2: Use sizeof (variable) not sizeof (type)
>>
>> diff --git a/fs/xfs/linux-2.6/xfs_ioctl.c b/fs/xfs/linux-2.6/xfs_ioctl.c
>> index f5e2a19..871e5f0 100644
>> --- a/fs/xfs/linux-2.6/xfs_ioctl.c
>> +++ b/fs/xfs/linux-2.6/xfs_ioctl.c
>> @@ -698,6 +698,7 @@ xfs_ioc_fsgeometry_v1(
>>   	xfs_fsop_geom_v1_t	fsgeo;
>>   	int			error;
>>
>> +	memset(&fsgeo, 0, sizeof(fsgeo));
>>   	error = xfs_fs_geometry(mp, (xfs_fsop_geom_t *)&fsgeo, 3);
>>   	if (error)
>>   		return -error;
>> @@ -715,6 +716,7 @@ xfs_ioc_fsgeometry(
>>   	xfs_fsop_geom_t		fsgeo;
>>   	int			error;
>>
>> +	memset(&fsgeo, 0, sizeof(fsgeo));
>>   	error = xfs_fs_geometry(mp,&fsgeo, 4);
>>   	if (error)
>>   		return -error;
>> diff --git a/fs/xfs/linux-2.6/xfs_ioctl32.c b/fs/xfs/linux-2.6/xfs_ioctl32.c
>> index b3486df..f25d38e 100644
>> --- a/fs/xfs/linux-2.6/xfs_ioctl32.c
>> +++ b/fs/xfs/linux-2.6/xfs_ioctl32.c
>> @@ -73,6 +73,7 @@ xfs_compat_ioc_fsgeometry_v1(
>>   	xfs_fsop_geom_t		  fsgeo;
>>   	int			  error;
>>
>> +	memset(&fsgeo, 0, sizeof(fsgeo));
>>   	error = xfs_fs_geometry(mp,&fsgeo, 3);
>>   	if (error)
>>   		return -error;
>> diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
>> index 85668ef..cec89dd 100644
>> --- a/fs/xfs/xfs_fsops.c
>> +++ b/fs/xfs/xfs_fsops.c
>> @@ -53,9 +53,6 @@ xfs_fs_geometry(
>>   	xfs_fsop_geom_t		*geo,
>>   	int			new_version)
>>   {
>> -
>> -	memset(geo, 0, sizeof(*geo));
>> -
>>   	geo->blocksize = mp->m_sb.sb_blocksize;
>>   	geo->rtextsize = mp->m_sb.sb_rextsize;
>>   	geo->agblocks = mp->m_sb.sb_agblocks;
>>      
>
>    

Hello,

I confirm that this patch DOES FIX the problem I was seeing with xfs_fsr 
that caused a hit on the stack-protector.

Thanks for your hard work!

Tested-by: Jeffrey Hundstad <jeffrey.hundstad@mnsu.edu>

-- 
Jeffrey Hundstad

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