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")
Reported-by: syzbot+a1c743815982d9496...@syzkaller.appspotmail.com
Tested-by: syzbot+a1c743815982d9496...@syzkaller.appspotmail.com
Link:
https://syzkaller.appspot.com/bug?id=9d2a7ca8c7f2e4b682c97578dfa3f236258300b3
Signed-off-by: Anmol Karn <anmol.karan...@gmail.com>
---
Changes in v4:
- Free `dev`(on dev_hold()), when neigh->dev is NULL. (Suggested-by:
Jakub Kicinski <k...@kernel.org>)
Changes in v3:
- Corrected checkpatch warnings and errors (Suggested-by: Saeed
Mahameed <sa...@kernel.org>)
- Added "Fixes:" tag (Suggested-by: Saeed Mahameed <sa...@kernel.org>)
Changes in v2:
- Added NULL check in rose_loopback_timer() (Suggested-by: Greg KH
<gre...@linuxfoundation.org>)
net/rose/rose_loopback.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/net/rose/rose_loopback.c b/net/rose/rose_loopback.c
index 7b094275ea8b..6a71b6947d92 100644
--- a/net/rose/rose_loopback.c
+++ b/net/rose/rose_loopback.c
@@ -96,10 +96,12 @@ static void rose_loopback_timer(struct timer_list *unused)
}
if (frametype == ROSE_CALL_REQUEST) {
- if ((dev = rose_dev_get(dest)) != NULL) {
+ dev = rose_dev_get(dest);
+ if (rose_loopback_neigh->dev && dev) {
if (rose_rx_call_request(skb, dev,
rose_loopback_neigh, lci_o) == 0)
kfree_skb(skb);
} else {
+ dev_put(dev);
kfree_skb(skb);
}
} else {
--
2.29.2
