linux-kernel - [PATCH 5.4 09/65] bpf, cgroup: Fix problematic bounds check

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Message-Id: <20210208145810.599465221@linuxfoundation.org>
Date:   Mon,  8 Feb 2021 16:00:41 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Loris Reiff <loris.reiff@...lor.ch>,
        Daniel Borkmann <daniel@...earbox.net>,
        Stanislav Fomichev <sdf@...gle.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 09/65] bpf, cgroup: Fix problematic bounds check

From: Loris Reiff <loris.reiff@...lor.ch>

[ Upstream commit f4a2da755a7e1f5d845c52aee71336cee289935a ]

Since ctx.optlen is signed, a larger value than max_value could be
passed, as it is later on used as unsigned, which causes a WARN_ON_ONCE
in the copy_to_user.

Fixes: 0d01da6afc54 ("bpf: implement getsockopt and setsockopt hooks")
Signed-off-by: Loris Reiff <loris.reiff@...lor.ch>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Reviewed-by: Stanislav Fomichev <sdf@...gle.com>
Link: https://lore.kernel.org/bpf/20210122164232.61770-2-loris.reiff@liblor.ch
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/bpf/cgroup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 5b2413eb79db4..c2f0aa818b7af 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -1131,7 +1131,7 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level,
 		goto out;
 	}
 
-	if (ctx.optlen > max_optlen) {
+	if (ctx.optlen > max_optlen || ctx.optlen < 0) {
 		ret = -EFAULT;
 		goto out;
 	}
-- 
2.27.0