netdev - [PATCH net v2] net: mvneta: Fix an out of bounds check

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Message-ID: <Y5A7d1E5ccwHTYPf@kadam>
Date:   Wed, 7 Dec 2022 10:06:31 +0300
From:   Dan Carpenter <error27@...il.com>
To:     Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Cc:     "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,
        kernel-janitors@...r.kernel.org
Subject: [PATCH net v2] net: mvneta: Fix an out of bounds check

In an earlier commit, I added a bounds check to prevent an out of bounds
read and a WARN().  On further discussion and consideration that check
was probably too aggressive.  Instead of returning -EINVAL, a better fix
would be to just prevent the out of bounds read but continue the process.

Background: The value of "pp->rxq_def" is a number between 0-7 by default,
or even higher depending on the value of "rxq_number", which is a module
parameter. If the value is more than the number of available CPUs then
it will trigger the WARN() in cpu_max_bits_warn().

Fixes: e8b4fc13900b ("net: mvneta: Prevent out of bounds read in mvneta_config_rss()")
Signed-off-by: Dan Carpenter <error27@...il.com>
---
v2: fix the subject to say net instead of net-next.

 drivers/net/ethernet/marvell/mvneta.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index 66b7f27c9a48..5aefaaff0871 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -4271,7 +4271,7 @@ static void mvneta_percpu_elect(struct mvneta_port *pp)
 	/* Use the cpu associated to the rxq when it is online, in all
 	 * the other cases, use the cpu 0 which can't be offline.
 	 */
-	if (cpu_online(pp->rxq_def))
+	if (pp->rxq_def < nr_cpu_ids && cpu_online(pp->rxq_def))
 		elected_cpu = pp->rxq_def;
 
 	max_cpu = num_present_cpus();
@@ -4927,9 +4927,6 @@ static int  mvneta_config_rss(struct mvneta_port *pp)
 		napi_disable(&pp->napi);
 	}
 
-	if (pp->indir[0] >= nr_cpu_ids)
-		return -EINVAL;
-
 	pp->rxq_def = pp->indir[0];
 
 	/* Update unicast mapping */
-- 
2.35.1