gigaset: fix bad assumptions about CAPI skbuffs

The CAPI interface incorrectly assumed that CAPI messages would always
start at the beginning of the data buffer: fix by treating DATA_B3
messages as the link layer header to their payload data. This fix
changes the way acknowledgement information is propagated through the
hardware specific modules and thereby impacts the ISDN4Linux variant
of the driver, too.

Also some assumptions about methods not being called from interrupt
context turned out to be unwarranted; fix by using dev_kfree_skb_any()
wherever non-interrupt context isn't guaranteed.

Impact: bugfix
Signed-off-by: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 20 insertions, 8 deletions

diff --git a/drivers/isdn/gigaset/i4l.c b/drivers/isdn/gigaset/i4l.c
index aca72a06184e..828824f905c4 100644
--- a/drivers/isdn/gigaset/i4l.c
+++ b/drivers/isdn/gigaset/i4l.c
@@ -41,8 +41,8 @@ static int writebuf_from_LL(int driverID, int channel, int ack,
 {
         struct cardstate *cs;
         struct bc_state *bcs;
+        unsigned char *ack_header;
         unsigned len;
-        unsigned skblen;
 
         if (!(cs = gigaset_get_cs_by_id(driverID))) {
                 pr_err("%s: invalid driver ID (%d)\n", __func__, driverID);
@@ -78,11 +78,23 @@ static int writebuf_from_LL(int driverID, int channel, int ack,
                 return -EINVAL;
         }
 
-        skblen = ack ? len : 0;
-        skb->head[0] = skblen & 0xff;
-        skb->head[1] = skblen >> 8;
-        gig_dbg(DEBUG_MCMD, "skb: len=%u, skblen=%u: %02x %02x",
-                len, skblen, (unsigned) skb->head[0], (unsigned) skb->head[1]);
+        /* set up acknowledgement header */
+        if (skb_headroom(skb) < HW_HDR_LEN) {
+                /* should never happen */
+                dev_err(cs->dev, "%s: insufficient skb headroom\n", __func__);
+                return -ENOMEM;
+        }
+        skb_set_mac_header(skb, -HW_HDR_LEN);
+        skb->mac_len = HW_HDR_LEN;
+        ack_header = skb_mac_header(skb);
+        if (ack) {
+                ack_header[0] = len & 0xff;
+                ack_header[1] = len >> 8;
+        } else {
+                ack_header[0] = ack_header[1] = 0;
+        }
+        gig_dbg(DEBUG_MCMD, "skb: len=%u, ack=%d: %02x %02x",
+                len, ack, ack_header[0], ack_header[1]);
 
         /* pass to device-specific module */
         return cs->ops->send_skb(bcs, skb);
@@ -99,6 +111,7 @@ static int writebuf_from_LL(int driverID, int channel, int ack,
 void gigaset_skb_sent(struct bc_state *bcs, struct sk_buff *skb)
 {
         isdn_if *iif = bcs->cs->iif;
+        unsigned char *ack_header = skb_mac_header(skb);
         unsigned len;
         isdn_ctrl response;
 
@@ -108,8 +121,7 @@ void gigaset_skb_sent(struct bc_state *bcs, struct sk_buff *skb)
                 dev_warn(bcs->cs->dev, "%s: skb->len==%d\n",
                          __func__, skb->len);
 
-        len = (unsigned char) skb->head[0] |
-              (unsigned) (unsigned char) skb->head[1] << 8;
+        len = ack_header[0] + ((unsigned) ack_header[1] << 8);
         if (len) {
                 gig_dbg(DEBUG_MCMD, "ACKing to LL (id: %d, ch: %d, sz: %u)",
                         bcs->cs->myid, bcs->channel, len);