Commit 3b3fd068 authored Nov 20, 2020 by Anmol Karn Committed by Jakub Kicinski Nov 20, 2020

rose: Fix Null pointer dereference in rose_send_frame()



rose_send_frame() dereferences `neigh->dev` when called from
rose_transmit_clear_request(), and the first occurrence of the
`neigh` is in rose_loopback_timer() as `rose_loopback_neigh`,
and it is initialized in rose_add_loopback_neigh() as NULL.
i.e when `rose_loopback_neigh` used in rose_loopback_timer()
its `->dev` was still NULL and rose_loopback_timer() was calling
rose_rx_call_request() without checking for NULL.

- net/rose/rose_link.c
This bug seems to get triggered in this line:

rose_call = (ax25_address *)neigh->dev->dev_addr;

Fix it by adding NULL checking for `rose_loopback_neigh->dev`
in rose_loopback_timer().

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Reported-by:  <syzbot+a1c743815982d9496393@syzkaller.appspotmail.com>
Tested-by:  <syzbot+a1c743815982d9496393@syzkaller.appspotmail.com>
Link: https://syzkaller.appspot.com/bug?id=9d2a7ca8c7f2e4b682c97578dfa3f236258300b3


Signed-off-by: Anmol Karn <anmol.karan123@gmail.com>
Link: https://lore.kernel.org/r/20201119191043.28813-1-anmol.karan123@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>

parent f46e79aa

net/rose/rose_loopback.c

+13 −4

Original line number	Diff line number	Diff line
		@@ -96,10 +96,19 @@ static void rose_loopback_timer(struct timer_list *unused)
		}

		if (frametype == ROSE_CALL_REQUEST) {
		if ((dev = rose_dev_get(dest)) != NULL) {
		if (rose_rx_call_request(skb, dev, rose_loopback_neigh, lci_o) == 0)
		if (!rose_loopback_neigh->dev) {
		kfree_skb(skb);
		} else {
		continue;
		}

		dev = rose_dev_get(dest);
		if (!dev) {
		kfree_skb(skb);
		continue;
		}

		if (rose_rx_call_request(skb, dev, rose_loopback_neigh, lci_o) == 0) {
		dev_put(dev);
		kfree_skb(skb);
		}
		} else {

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