Here's a patch to fix a bug in compat_sys_fcntl64 in fs/compat.c.  The bug
occurs with a 32 bit app that calls fcntl and checking for a lock near the
end of a file.

    struct flock sflp;
    sflp.l_start = 2147483345;
    sflp.l_len = 302;
    /* 2147483345 + 302 == 2147483647 (this should not overflow 31 bits) */
    /* 2^31 ==             2147483648 */
    fcntl_stat = fcntl(fd, F_GETLK, &sflp);

The patch also contains a fix to handle l_len < 0 which is now defined in
POSIX 1003.1-2001 from the fcntl man page.
Signed-off-by: John Engel <jhe@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>