linux-kernel - [PATCH AUTOSEL 6.1 34/35] prlimit: do_prlimit needs to have a speculation check

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Message-Id: <20230124134131.637036-34-sashal@kernel.org>
Date:   Tue, 24 Jan 2023 08:41:30 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jordy Zomer <jordyzomer@...gle.com>,
        Linus Torvalds <torvalds@...uxfoundation.org>,
        Sasha Levin <sashal@...nel.org>, ebiederm@...ssion.com,
        brho@...gle.com, catalin.marinas@....com, broonie@...nel.org,
        legion@...nel.org, Jason@...c4.com, surenb@...gle.com
Subject: [PATCH AUTOSEL 6.1 34/35] prlimit: do_prlimit needs to have a speculation check

From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

[ Upstream commit 739790605705ddcf18f21782b9c99ad7d53a8c11 ]

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@...gle.com>
Tested-by: Jordy Zomer <jordyzomer@...gle.com>
Suggested-by: Linus Torvalds <torvalds@...uxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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;
-- 
2.39.0