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net: lapb: Copy the skb before sending a packet
[ Upstream commit88c7a9fd9b
] When sending a packet, we will prepend it with an LAPB header. This modifies the shared parts of a cloned skb, so we should copy the skb rather than just clone it, before we prepend the header. In "Documentation/networking/driver.rst" (the 2nd point), it states that drivers shouldn't modify the shared parts of a cloned skb when transmitting. The "dev_queue_xmit_nit" function in "net/core/dev.c", which is called when an skb is being sent, clones the skb and sents the clone to AF_PACKET sockets. Because the LAPB drivers first remove a 1-byte pseudo-header before handing over the skb to us, if we don't copy the skb before prepending the LAPB header, the first byte of the packets received on AF_PACKET sockets can be corrupted. Fixes:1da177e4c3
("Linux-2.6.12-rc2") Signed-off-by: Xie He <xie.he.0141@gmail.com> Acked-by: Martin Schiller <ms@dev.tdt.de> Link: https://lore.kernel.org/r/20210201055706.415842-1-xie.he.0141@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
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1 changed files with 2 additions and 1 deletions
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@ -82,7 +82,8 @@ void lapb_kick(struct lapb_cb *lapb)
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skb = skb_dequeue(&lapb->write_queue);
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skb = skb_dequeue(&lapb->write_queue);
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do {
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do {
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if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
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skbn = skb_copy(skb, GFP_ATOMIC);
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if (!skbn) {
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skb_queue_head(&lapb->write_queue, skb);
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skb_queue_head(&lapb->write_queue, skb);
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break;
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break;
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}
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}
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