linux-kernel - [PATCH AUTOSEL 5.15 13/17] net: sched: sch: Bounds check priority

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Message-Id: <20230209111731.1892569-13-sashal@kernel.org>
Date:   Thu,  9 Feb 2023 06:17:25 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        Simon Horman <simon.horman@...igine.com>,
        Cong Wang <cong.wang@...edance.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 5.15 13/17] net: sched: sch: Bounds check priority

From: Kees Cook <keescook@...omium.org>

[ Upstream commit de5ca4c3852f896cacac2bf259597aab5e17d9e3 ]

Nothing was explicitly bounds checking the priority index used to access
clpriop[]. WARN and bail out early if it's pathological. Seen with GCC 13:

../net/sched/sch_htb.c: In function 'htb_activate_prios':
../net/sched/sch_htb.c:437:44: warning: array subscript [0, 31] is outside array bounds of 'struct htb_prio[8]' [-Warray-bounds=]
  437 |                         if (p->inner.clprio[prio].feed.rb_node)
      |                             ~~~~~~~~~~~~~~~^~~~~~
../net/sched/sch_htb.c:131:41: note: while referencing 'clprio'
  131 |                         struct htb_prio clprio[TC_HTB_NUMPRIO];
      |                                         ^~~~~~

Cc: Jamal Hadi Salim <jhs@...atatu.com>
Cc: Cong Wang <xiyou.wangcong@...il.com>
Cc: Jiri Pirko <jiri@...nulli.us>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Jakub Kicinski <kuba@...nel.org>
Cc: Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
Reviewed-by: Simon Horman <simon.horman@...igine.com>
Reviewed-by: Cong Wang <cong.wang@...edance.com>
Link: https://lore.kernel.org/r/20230127224036.never.561-kees@kernel.org
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/sched/sch_htb.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index 45b92e40082ef..7ea8c73ddeff0 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -427,7 +427,10 @@ static void htb_activate_prios(struct htb_sched *q, struct htb_class *cl)
 	while (cl->cmode == HTB_MAY_BORROW && p && mask) {
 		m = mask;
 		while (m) {
-			int prio = ffz(~m);
+			unsigned int prio = ffz(~m);
+
+			if (WARN_ON_ONCE(prio > ARRAY_SIZE(p->inner.clprio)))
+				break;
 			m &= ~(1 << prio);
 
 			if (p->inner.clprio[prio].feed.rb_node)
-- 
2.39.0