kern/123095 kern/131602 sendfile

[Andriy Gapon]

Not an expert by any measure but the following looks suspicious:
m_copy/m_copym calls mb_dupcl for M_EXT case and M_RDONLY is _not_ checked nor
preserved in that case.
So we may get a writable M_EXT mbuf pointing to sf_buf wrapping a page of a file.
But I am not sure if/how mbufs are re-used and if we can end up actually writing
something to the resulting mbuf.

-- 
Andriy Gapon