Re: [34-longterm 238/247] xfs: prevent leaking uninitialized stack memory in FSGEOMETRY_V1

Paul Gortmaker
2011-06-23T18:19:56Z

On Thu, Jun 23, 2011 at 1:49 PM, Dan Rosenberg <drosenberg@vsecurity.com> wrote:
> On Thu, 2011-06-23 at 13:35 -0400, Paul Gortmaker wrote:
>> From: Dan Rosenberg <drosenberg@vsecurity.com>
>>
>>                    -------------------
>>     This is a commit scheduled for the next v2.6.34 longterm release.
>>     If you see a problem with using this for longterm, please comment.
>>                    -------------------
>>
>> commit 3a3675b7f23f83ca8c67c9c2b6edf707fd28d1ba upstream.
>>
>> The FSGEOMETRY_V1 ioctl (and its compat equivalent) calls out to
>> xfs_fs_geometry() with a version number of 3.  This code path does not
>> fill in the logsunit member of the passed xfs_fsop_geom_t, leading to
>> the leaking of four bytes of uninitialized stack data to potentially
>> unprivileged callers.
>>
>> v2 switches to memset() to avoid future issues if structure members
>> change, on suggestion of Dave Chinner.
>>
>> Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>
>> Reviewed-by: Eugene Teo <eugeneteo@kernel.org>
>> Signed-off-by: Alex Elder <aelder@sgi.com>
>> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
>> ---
>>  fs/xfs/xfs_fsops.c |    3 +++
>>  1 files changed, 3 insertions(+), 0 deletions(-)
>>
>> diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
>> index 37a6f62..4e7f02b 100644
>> --- a/fs/xfs/xfs_fsops.c
>> +++ b/fs/xfs/xfs_fsops.c
>> @@ -57,6 +57,9 @@ 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;
>> --
>> 1.7.4.4
>
> This introduced a regression which was fixed by commit
> af24ee9ea8d532e16883251a6684dfa1be8eec29.

Thanks Dan,

Fix queued and will appear shortly here.

http://git.kernel.org/?p=linux/kernel/git/longterm/longterm-queue-2.6.34.git;a=summary

Paul.

>
> -Dan
>
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