linux-kernel - [PATCH] srcu: The value may overflow

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Message-Id: <20230901095341.55857-1-arefev@swemel.ru>
Date:   Fri,  1 Sep 2023 12:53:41 +0300
From:   Denis Arefev <arefev@...mel.ru>
To:     Lai Jiangshan <jiangshanlai@...il.com>
Cc:     "Paul E. McKenney" <paulmck@...nel.org>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        rcu@...r.kernel.org, lvc-project@...uxtesting.org,
        linux-kernel@...r.kernel.org, trufanov@...mel.ru, vfh@...mel.ru
Subject: [PATCH] srcu: The value may overflow

The value of an arithmetic expression 1 << (cpu - sdp->mynode->grplo)
is subject to overflow due to a failure to cast operands to a larger
data type before performing arithmetic

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Denis Arefev <arefev@...mel.ru>
---
 kernel/rcu/srcutree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 20d7a238d675..e14b74fb1ba0 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -223,7 +223,7 @@ static bool init_srcu_struct_nodes(struct srcu_struct *ssp, gfp_t gfp_flags)
 				snp->grplo = cpu;
 			snp->grphi = cpu;
 		}
-		sdp->grpmask = 1 << (cpu - sdp->mynode->grplo);
+		sdp->grpmask = 1UL << (cpu - sdp->mynode->grplo);
 	}
 	smp_store_release(&ssp->srcu_sup->srcu_size_state, SRCU_SIZE_WAIT_BARRIER);
 	return true;
-- 
2.25.1