The _xfs_buf_find function in fs/xfs/xfs_buf.c in the Linux kernel before 3.7.6 does not validate block numbers, which allows local users to cause a denial of service (NULL pointer dereference and system crash) or possibly have unspecified other impact by leveraging the ability to mount an XFS filesystem containing a metadata inode with an invalid extent map. A failure to validate block numbers was discovered in the Linux kernel's implementation of the XFS filesystem. A local user can cause a denial of service (system crash) if they can mount, or cause to be mounted a corrupted or special crafted XFS filesystem.