[PATCH] xfs: prevent reading uninitialized stack memory

[Dan Rosenberg <dan.j.rosenberg@xxxxxxxxx>]

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>

--- linux-2.6.35.4.orig/fs/xfs/linux-2.6/xfs_ioctl.c    2010-09-06
17:57:16.000000000 -0400
+++ linux-2.6.35.4/fs/xfs/linux-2.6/xfs_ioctl.c 2010-09-06
17:58:19.000000000 -0400
@@ -794,6 +794,8 @@ 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;