tree 5b913efe916dde0f9f1401b62bbcf373323dcf43
parent 3251c97f66407c57089c2002228fe25316ad4c57
author Peter Zijlstra <peterz@infradead.org> 1583317711 +0100
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1585840827 +0200

futex: Fix inode life-time issue

commit 8019ad13ef7f64be44d4f892af9c840179009254 upstream.

As reported by Jann, ihold() does not in fact guarantee inode
persistence. And instead of making it so, replace the usage of inode
pointers with a per boot, machine wide, unique inode identifier.

This sequence number is global, but shared (file backed) futexes are
rare enough that this should not become a performance issue.

Reported-by: Jann Horn <jannh@google.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>