linux-kernel - [PATCH] rcu: shift by 1UL rather than 1 to fix sign extension error

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Date:   Tue, 13 Dec 2016 10:56:46 +0000
From:   Colin King <colin.king@...onical.com>
To:     Boqun Feng <boqun.feng@...il.com>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] rcu: shift by 1UL rather than 1 to fix sign extension error

From: Colin Ian King <colin.king@...onical.com>

mask and bit are unsigned longs, so if bit is 31 we end up sign
extending the 1 and mask ends up as 0xffffffff80000000. Fix this
by explicitly adding integer suffix UL ensure 1 is a unsigned long
rather than an signed int.

Issue found with static analysis with CoverityScan, CID 1388564

Fixes: 8965c3ce4718754db ("rcu: Use leaf_node_for_each_mask_possible_cpu() in force_qs_rnp()")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 kernel/rcu/tree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 10162ac..6ecedd8 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3051,7 +3051,7 @@ static void force_qs_rnp(struct rcu_state *rsp,
 
 		leaf_node_for_each_mask_possible_cpu(rnp, rnp->qsmask, bit, cpu)
 			if (f(per_cpu_ptr(rsp->rda, cpu), isidle, maxj))
-				mask |= 1 << bit;
+				mask |= 1UL << bit;
 
 		if (mask != 0) {
 			/* Idle/offline CPUs, report (releases rnp->lock. */
-- 
2.10.2