xfs: prevent leaking uninitialized stack memory in FSGEOMETRY_V1

commit c4d0c3b097f7584772316ee4d64a09fe0e4ddfca 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: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index 6f83f58c099fee2db91d80f6d31c51f3b46f6830..785b2a2016e5cba9e787ee5844c52a79d2a5b090 100644 (file)
--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -56,6 +56,9 @@ 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;