K 10
svn:author
V 6
kevans
K 8
svn:date
V 27
2021-01-24T03:19:38.289638Z
K 7
svn:log
V 740
kern: dup: do not assume oldfde is valid

oldfde may be invalidated if the table has grown due to the operation that
we're performing, either via fdalloc() or a direct fdgrowtable_exp().

This was technically OK before rS367927 because the old table remained valid
until the filedesc became unused, but now it may be freed immediately if
it's an unshared table in a single-threaded process, so it is no longer a
good assumption to make.

This fixes dup/dup2 invocations that grow the file table; in the initial
report, it manifested as a kernel panic in devel/gmake's configure script.

(cherry picked from commit f96078b8fe55c944f32c3c82ebb9c360bc155823)

Git Hash:   fd478d518f49084e5bc4ff3ee0ae020c8db42b9e
Git Author: kevans@FreeBSD.org
END