[34-longterm 143/260] xfs: prevent reading uninitialized stack memory

[Paul Gortmaker]

From: Dan Rosenberg <dan.j.rosenberg@xxxxxxxxx>

commit a122eb2fdfd78b58c6dd992d6f4b1aaef667eef9 upstream.

The XFS_IOC_FSGETXATTR ioctl allows unprivileged users to read 12
bytes of uninitialized stack memory, because the fsxattr struct
declared on the stack in xfs_ioc_fsgetxattr() does not alter (or zero)
the 12-byte fsx_pad member before copying it back to the user.  This
patch takes care of it.

Signed-off-by: Dan Rosenberg <dan.j.rosenberg@xxxxxxxxx>
Reviewed-by: Eric Sandeen <sandeen@xxxxxxxxxx>
Signed-off-by: Alex Elder <aelder@xxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
 fs/xfs/linux-2.6/xfs_ioctl.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_ioctl.c b/fs/xfs/linux-2.6/xfs_ioctl.c
index 7b26cc2..3da1da7 100644
--- a/fs/xfs/linux-2.6/xfs_ioctl.c
+++ b/fs/xfs/linux-2.6/xfs_ioctl.c
@@ -791,6 +791,8 @@ xfs_ioc_fsgetxattr(
 {
 	struct fsxattr		fa;
 
+	memset(&fa, 0, sizeof(struct fsxattr));
+
 	xfs_ilock(ip, XFS_ILOCK_SHARED);
 	fa.fsx_xflags = xfs_ip2xflags(ip);
 	fa.fsx_extsize = ip->i_d.di_extsize << ip->i_mount->m_sb.sb_blocklog;
-- 
1.7.3.3

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