From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Fri, 20 Jan 2023 11:03:20 +0100
Subject: prlimit: do_prlimit needs to have a speculation check
Git-commit: 739790605705ddcf18f21782b9c99ad7d53a8c11
Patch-mainline: v6.2-rc5
References: bsc#1209256 CVE-2017-5753

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>
Acked-by: Michal Koutný <mkoutny@suse.com>
---
 kernel/sys.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sys.c b/kernel/sys.c
index 5fd54bf0e886..88b31f096fb2 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1442,6 +1442,8 @@ static int do_prlimit(struct task_struct *tsk, unsigned int resource,
 
 	if (resource >= RLIM_NLIMITS)
 		return -EINVAL;
+	resource = array_index_nospec(resource, RLIM_NLIMITS);
+
 	if (new_rlim) {
 		if (new_rlim->rlim_cur > new_rlim->rlim_max)
 			return -EINVAL;