Merge branch 'dst_cache-fix-possible-races'

Eric Dumazet says:

====================
dst_cache: fix possible races

This series is inspired by various undisclosed syzbot
reports hinting at corruptions in dst_cache structures.

It seems at least four users of dst_cache are racy against
BH reentrancy.

Last patch is adding a DEBUG_NET check to catch future misuses.
====================

Link: https://lore.kernel.org/r/20240531132636.2637995-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>