xfs: add capability check to free eofblocks ioctl

commit 8c567a7fab6e086a0284eee2db82348521e7120c upstream.

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@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Gao feng <gaofeng@cn.fujitsu.com>
Signed-off-by: Dwight Engen <dwight.engen@oracle.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
Cc: Kees Cook <keescook@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 668e8f4ccf5e7201e8e6a360cd26668484f6d515..2e1e6c33841d2ca7920fd6b25fdd8858e7397014 100644 (file)
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -1711,6 +1711,12 @@ 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 (!capable(CAP_SYS_ADMIN))
                        return -EPERM;