From: Anmol Karn <anmol.karan123@xxxxxxxxx>
[ Upstream commit 3b3fd068c56e3fbea30090859216a368398e39bf ]
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: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Suggested-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Reported-by: syzbot+a1c743815982d9496393@xxxxxxxxxxxxxxxxxxxxxxxxx
Tested-by: syzbot+a1c743815982d9496393@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://syzkaller.appspot.com/bug?id=9d2a7ca8c7f2e4b682c97578dfa3f236258300b3
Signed-off-by: Anmol Karn <anmol.karan123@xxxxxxxxx>
Link: https://lore.kernel.org/r/20201119191043.28813-1-anmol.karan123@xxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/rose/rose_loopback.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
--- a/net/rose/rose_loopback.c
+++ b/net/rose/rose_loopback.c
@@ -96,10 +96,19 @@ static void rose_loopback_timer(struct t
}
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)
- kfree_skb(skb);
- } else {
+ if (!rose_loopback_neigh->dev) {
+ kfree_skb(skb);
+ 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 {
