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| author | Xie He <xie.he.0141@gmail.com> | 2020-07-24 18:33:47 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2020-07-25 05:17:42 +0200 |
| commit | 8754e1379e7089516a449821f88e1fe1ebbae5e1 (patch) | |
| tree | 74685b4cf69609691e2fd968655cdecf43fb04cf | |
| parent | dev: Defer free of skbs in flush_backlog (diff) | |
| download | linux-8754e1379e7089516a449821f88e1fe1ebbae5e1.tar.xz linux-8754e1379e7089516a449821f88e1fe1ebbae5e1.zip | |
drivers/net/wan: lapb: Corrected the usage of skb_cow
This patch fixed 2 issues with the usage of skb_cow in LAPB drivers
"lapbether" and "hdlc_x25":
1) After skb_cow fails, kfree_skb should be called to drop a reference
to the skb. But in both drivers, kfree_skb is not called.
2) skb_cow should be called before skb_push so that is can ensure the
safety of skb_push. But in "lapbether", it is incorrectly called after
skb_push.
More details about these 2 issues:
1) The behavior of calling kfree_skb on failure is also the behavior of
netif_rx, which is called by this function with "return netif_rx(skb);".
So this function should follow this behavior, too.
2) In "lapbether", skb_cow is called after skb_push. This results in 2
logical issues:
a) skb_push is not protected by skb_cow;
b) An extra headroom of 1 byte is ensured after skb_push. This extra
headroom has no use in this function. It also has no use in the
upper-layer function that this function passes the skb to
(x25_lapb_receive_frame in net/x25/x25_dev.c).
So logically skb_cow should instead be called before skb_push.
Cc: Eric Dumazet <edumazet@google.com>
Cc: Martin Schiller <ms@dev.tdt.de>
Signed-off-by: Xie He <xie.he.0141@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | drivers/net/wan/hdlc_x25.c | 4 | ||||
| -rw-r--r-- | drivers/net/wan/lapbether.c | 8 |
2 files changed, 8 insertions, 4 deletions
diff --git a/drivers/net/wan/hdlc_x25.c b/drivers/net/wan/hdlc_x25.c index c84536b03aa8..f70336bb6f52 100644 --- a/drivers/net/wan/hdlc_x25.c +++ b/drivers/net/wan/hdlc_x25.c @@ -71,8 +71,10 @@ static int x25_data_indication(struct net_device *dev, struct sk_buff *skb) { unsigned char *ptr; - if (skb_cow(skb, 1)) + if (skb_cow(skb, 1)) { + kfree_skb(skb); return NET_RX_DROP; + } skb_push(skb, 1); skb_reset_network_header(skb); diff --git a/drivers/net/wan/lapbether.c b/drivers/net/wan/lapbether.c index 284832314f31..b2868433718f 100644 --- a/drivers/net/wan/lapbether.c +++ b/drivers/net/wan/lapbether.c @@ -128,10 +128,12 @@ static int lapbeth_data_indication(struct net_device *dev, struct sk_buff *skb) { unsigned char *ptr; - skb_push(skb, 1); - - if (skb_cow(skb, 1)) + if (skb_cow(skb, 1)) { + kfree_skb(skb); return NET_RX_DROP; + } + + skb_push(skb, 1); ptr = skb->data; *ptr = X25_IFACE_DATA; |