[GIT PULL] proc fix for 5.7-rc1

[Eric W. Biederman]

Linus,

Please pull the for-linus branch from the git tree:

   git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace.git for-linus

   HEAD: 63f818f46af9f8b3f17b9695501e8d08959feb60 proc: Use a dedicated lock in struct pid

A brown paper bag slipped through my proc changes, and syzcaller caught
it when the code ended up in your tree.  I have opted to fix it the
simplest cleanest way I know how.  So there is no reasonable chance
for the bug to repeat.

Eric