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[PATCH v2] xfs: prevent leaking uninitialized stack memory in FSGEOMETRY

To: Dave Chinner <david@xxxxxxxxxxxxx>, aelder@xxxxxxx, xfs-masters@xxxxxxxxxxx, xfs@xxxxxxxxxxx
Subject: [PATCH v2] xfs: prevent leaking uninitialized stack memory in FSGEOMETRY_V1
From: Dan Rosenberg <drosenberg@xxxxxxxxxxxxx>
Date: Mon, 14 Feb 2011 08:45:28 -0500
Cc: linux-kernel@xxxxxxxxxxxxxxx, stable@xxxxxxxxxx, security@xxxxxxxxxx
In-reply-to: <20110214114629.GA13052@dastard>
References: <1297347904.13370.9.camel@dan> <20110214114629.GA13052@dastard>
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@xxxxxxxxxxxxx>
 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 cec89dd..85668ef 100644
--- 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;

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