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From: Christian Eggers <ceggers@arri.de>
To: Woojung Huh <woojung.huh@microchip.com>,
	Andrew Lunn <andrew@lunn.ch>,
	Vivien Didelot <vivien.didelot@gmail.com>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Vladimir Oltean <olteanv@gmail.com>
Cc: Microchip Linux Driver Support <UNGLinuxDriver@microchip.com>,
	"David S . Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>, <netdev@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>,
	Christian Eggers <ceggers@arri.de>
Subject: [PATCH net] net: dsa: ksz: fix padding size of skb
Date: Wed, 14 Oct 2020 18:17:19 +0200
Message-ID: <20201014161719.30289-1-ceggers@arri.de> (raw)

__skb_put_padto() is called in order to ensure a minimal size of the
sk_buff. The required minimal size is ETH_ZLEN + the size required for
the tail tag.

The current argument misses the size for the tail tag. The expression
"skb->len + padlen" can be simplified to ETH_ZLEN.

Too small sk_buffs typically result from cloning in
dsa_skb_tx_timestamp(). The cloned sk_buff may not meet the minimum size
requirements.

Fixes: e71cb9e00922 ("net: dsa: ksz: fix skb freeing")
Signed-off-by: Christian Eggers <ceggers@arri.de>
---
 net/dsa/tag_ksz.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/dsa/tag_ksz.c b/net/dsa/tag_ksz.c
index 945a9bd5ba35..8ef2085349e7 100644
--- a/net/dsa/tag_ksz.c
+++ b/net/dsa/tag_ksz.c
@@ -24,7 +24,7 @@ static struct sk_buff *ksz_common_xmit(struct sk_buff *skb,
 
 	if (skb_tailroom(skb) >= padlen + len) {
 		/* Let dsa_slave_xmit() free skb */
-		if (__skb_put_padto(skb, skb->len + padlen, false))
+		if (__skb_put_padto(skb, ETH_ZLEN + len, false))
 			return NULL;
 
 		nskb = skb;
@@ -45,7 +45,7 @@ static struct sk_buff *ksz_common_xmit(struct sk_buff *skb,
 		/* Let skb_put_padto() free nskb, and let dsa_slave_xmit() free
 		 * skb
 		 */
-		if (skb_put_padto(nskb, nskb->len + padlen))
+		if (skb_put_padto(nskb, ETH_ZLEN + len))
 			return NULL;
 
 		consume_skb(skb);
-- 
Christian Eggers
Embedded software developer

Arnold & Richter Cine Technik GmbH & Co. Betriebs KG
Sitz: Muenchen - Registergericht: Amtsgericht Muenchen - Handelsregisternummer: HRA 57918
Persoenlich haftender Gesellschafter: Arnold & Richter Cine Technik GmbH
Sitz: Muenchen - Registergericht: Amtsgericht Muenchen - Handelsregisternummer: HRB 54477
Geschaeftsfuehrer: Dr. Michael Neuhaeuser; Stephan Schenk; Walter Trauninger; Markus Zeiler


             reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-14 16:17 Christian Eggers [this message]
2020-10-14 16:47 ` Vladimir Oltean
2020-10-14 16:54   ` Vladimir Oltean
2020-10-14 17:02     ` Christian Eggers
2020-10-14 17:31       ` Vladimir Oltean
2020-10-15 17:58         ` Christian Eggers
2020-10-16  7:45           ` Kurt Kanzenbach
2020-10-16  9:00             ` Christian Eggers
2020-10-16  9:05               ` Vladimir Oltean
2020-10-16 12:44                 ` Christian Eggers
2020-10-16 15:56                   ` Vladimir Oltean
2020-10-16 18:03                     ` Jakub Kicinski
2020-10-16 18:13                       ` Vladimir Oltean
2020-10-16 18:52                         ` Jakub Kicinski

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