From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Fri, 20 Jan 2023 10:03:20 +0000 (+0100)
Subject: prlimit: do_prlimit needs to have a speculation check
X-Git-Tag: baikal/aarch64/sdk5.9~169
X-Git-Url: https://git.baikalelectronics.ru/sdk/?a=commitdiff_plain;h=94528a2fd242ba2ed4cba5b9f803b5d88101303b;p=kernel.git

prlimit: do_prlimit needs to have a speculation check

commit 739790605705ddcf18f21782b9c99ad7d53a8c11 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>
---

diff --git a/kernel/sys.c b/kernel/sys.c
index b075fe84eb5a5..f6d6ce8da3e4a 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1534,6 +1534,8 @@ 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;