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xfs: fix type confusion in xfs_ioc_swapext 

When calling fdget() in xfs_ioc_swapext(), we need to verify that
the file descriptors passed into the ioctl point to XFS inodes
before we start operations on them. If we don't do this, we could be
referencing arbitrary kernel memory as an XFS inode. THis could lead
to memory corruption and/or performing locking operations on
attacker-chosen structures in kernel memory.

[dchinner: rewrite commit message ]
[dchinner: add comment explaining new check ]

Signed-off-by: Jann Horn <jann@thejh.net>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Jann Horn 2016-07-20 10:30:30 +10:00 committed by Dave Chinner
parent 1a695a905c
commit 7f1b62457b
1 changed files with 11 additions and 0 deletions
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11
fs/xfs/xfs_ioctl.c
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@ -1575,6 +1575,17 @@ xfs_ioc_swapext(
goto out_put_tmp_file;
}
/*
* We need to ensure that the fds passed in point to XFS inodes
* before we cast and access them as XFS structures as we have no
* control over what the user passes us here.
*/
if (f.file->f_op != &xfs_file_operations ||
tmp.file->f_op != &xfs_file_operations) {
error = -EINVAL;
goto out_put_tmp_file;
}
ip = XFS_I(file_inode(f.file));
tip = XFS_I(file_inode(tmp.file));