xfs: prevent leaking uninitialized stack memory in FSGEOMETRY_V1

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>

diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index cec89dd5d7d28262ae064e257ec941a815cbb09f..85668efb3e3e03221b5e6dd3f517ad2e38b16f94 100644 (file)
--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -53,6 +53,9 @@ 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;