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[PATCH v8 6/7] xfs: add capability check to free eofblocks ioctl

To: xfs@xxxxxxxxxxx
Subject: [PATCH v8 6/7] xfs: add capability check to free eofblocks ioctl
From: Dwight Engen <dwight.engen@xxxxxxxxxx>
Date: Thu, 15 Aug 2013 14:08:03 -0400
Cc: Ben Myers <bpm@xxxxxxx>, Dave Chinner <david@xxxxxxxxxxxxx>, Dwight Engen <dwight.engen@xxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1376590084-12888-1-git-send-email-dwight.engen@xxxxxxxxxx>
References: <1376590084-12888-1-git-send-email-dwight.engen@xxxxxxxxxx>
Check for CAP_SYS_ADMIN since the caller can truncate preallocated
blocks from files they do not own nor have write access to. A more
fine grained access check was considered: require the caller to
specify their own uid/gid and to use inode_permission to check for
write, but this would not catch the case of an inode not reachable
via path traversal from the callers mount namespace.

Add check for read-only filesystem to free eofblocks ioctl.

Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>
Reviewed-by: Gao feng <gaofeng@xxxxxxxxxxxxxx>
Signed-off-by: Dwight Engen <dwight.engen@xxxxxxxxxx>
 fs/xfs/xfs_ioctl.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 20b4c7a..bdebc21 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -1723,6 +1723,12 @@ xfs_file_ioctl(
                struct xfs_fs_eofblocks eofb;
                struct xfs_eofblocks keofb;
+               if (!capable(CAP_SYS_ADMIN))
+                       return -EPERM;
+               if (mp->m_flags & XFS_MOUNT_RDONLY)
+                       return -XFS_ERROR(EROFS);
                if (copy_from_user(&eofb, arg, sizeof(eofb)))
                        return -XFS_ERROR(EFAULT);

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