namei: ->d_inode of a pinned dentry is stable only for positives

commit d4565649b6 upstream.

both do_last() and walk_component() risk picking a NULL inode out
of dentry about to become positive, *then* checking its flags and
seeing that it's not negative anymore and using (already stale by
then) value they'd fetched earlier.  Usually ends up oopsing soon
after that...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Al Viro 2016-02-27 19:23:16 -05:00 • committed by Greg Kroah-Hartman
commit aaf1569ce4