Eric Lee / smarc-ti-linux-kernel

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Commit 6ab8d4d1eb6a7db792397e4a6a61a5a0a51a7411

Authored by Ahmed S. Darwish
Committed by Greg Kroah-Hartman
1 parent 97ab28073b
Exists in smarc-ti-linux-3.14.y and in 1 other branch processor-sdk-linux-01.00.00

can: kvaser_usb: Don't free packets when tight on URBs 

commit b442723fcec445fb0ae1104888dd22cd285e0a91 upstream.

Flooding the Kvaser CAN to USB dongle with multiple reads and
writes in high frequency caused seemingly-random panics in the
kernel.

On further inspection, it seems the driver erroneously freed the
to-be-transmitted packet upon getting tight on URBs and returning
NETDEV_TX_BUSY, leading to invalid memory writes and double frees
at a later point in time.

Note:

Finding no more URBs/transmit-contexts and returning NETDEV_TX_BUSY
is a driver bug in and out of itself: it means that our start/stop
queue flow control is broken.

This patch only fixes the (buggy) error handling code; the root
cause shall be fixed in a later commit.

Acked-by: Olivier Sobrie <olivier@sobrie.be>
Signed-off-by: Ahmed S. Darwish <ahmed.darwish@valeo.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Showing 1 changed file with 4 additions and 6 deletions Side-by-side Diff

drivers/net/can/usb/kvaser_usb.c
Diff comments   View file @ 6ab8d4d
... ... @@ -1285,12 +1285,14 @@
1285 1285 if (!urb) {
1286 1286 netdev_err(netdev, "No memory left for URBs\n");
1287 1287 stats->tx_dropped++;
1288   - goto nourbmem;
  1288 + dev_kfree_skb(skb);
  1289 + return NETDEV_TX_OK;
1289 1290 }
1290 1291  
1291 1292 buf = kmalloc(sizeof(struct kvaser_msg), GFP_ATOMIC);
1292 1293 if (!buf) {
1293 1294 stats->tx_dropped++;
  1295 + dev_kfree_skb(skb);
1294 1296 goto nobufmem;
1295 1297 }
1296 1298  
... ... @@ -1325,6 +1327,7 @@
1325 1327 }
1326 1328 }
1327 1329  
  1330 + /* This should never happen; it implies a flow control bug */
1328 1331 if (!context) {
1329 1332 netdev_warn(netdev, "cannot find free context\n");
1330 1333 ret = NETDEV_TX_BUSY;
... ... @@ -1355,9 +1358,6 @@
1355 1358 if (unlikely(err)) {
1356 1359 can_free_echo_skb(netdev, context->echo_index);
1357 1360  
1358   - skb = NULL; /* set to NULL to avoid double free in
1359   - * dev_kfree_skb(skb) */
1360   -
1361 1361 atomic_dec(&priv->active_tx_urbs);
1362 1362 usb_unanchor_urb(urb);
1363 1363  
... ... @@ -1379,8 +1379,6 @@
1379 1379 kfree(buf);
1380 1380 nobufmem:
1381 1381 usb_free_urb(urb);
1382   -nourbmem:
1383   - dev_kfree_skb(skb);
1384 1382 return ret;
1385 1383 }
1386 1384