prlimit: do_prlimit needs to have a speculation check

stable inclusion
from stable-v4.19.271
commit d3ee91e50a6b3c5a45398e3dcb912a8a264f575c
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6DPF8


CVE: NA

--------------------------------

commit 73979060 upstream.

do_prlimit() adds the user-controlled resource value to a pointer that
will subsequently be dereferenced.  In order to help prevent this
codepath from being used as a spectre "gadget" a barrier needs to be
added after checking the range.

Reported-by: Jordy Zomer <jordyzomer@google.com>
Tested-by: Jordy Zomer <jordyzomer@google.com>
Suggested-by: Linus Torvalds <torvalds@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>