[PATCH 4.19 11/56] rose: check NULL rose_loopback_neigh->loopback

Greg Kroah-Hartman
2022-09-02T12:30:57Z

From: Bernard Pidoux <f6bvp@free.fr>

[ Upstream commit 3c53cd65dece47dd1f9d3a809f32e59d1d87b2b8 ]

Commit 3b3fd068c56e3fbea30090859216a368398e39bf added NULL check for
`rose_loopback_neigh->dev` in rose_loopback_timer() but omitted to
check rose_loopback_neigh->loopback.

It thus prevents *all* rose connect.

The reason is that a special rose_neigh loopback has a NULL device.

/proc/net/rose_neigh illustrates it via rose_neigh_show() function :
[...]
seq_printf(seq, "%05d %-9s %-4s %3d %3d %3s %3s %3lu %3lu",
rose_neigh->number,
(rose_neigh->loopback) ? "RSLOOP-0" : ax2asc(buf, &rose_neigh->callsign),
rose_neigh->dev ? rose_neigh->dev->name : "???",
rose_neigh->count,

/proc/net/rose_neigh displays special rose_loopback_neigh->loopback as
callsign RSLOOP-0:

addr callsign dev count use mode restart t0 tf digipeaters
00001 RSLOOP-0 ??? 1 2 DCE yes 0 0

By checking rose_loopback_neigh->loopback, rose_rx_call_request() is called
even in case rose_loopback_neigh->dev is NULL. This repairs rose connections.

Verification with rose client application FPAC:

FPAC-Node v 4.1.3 (built Aug 5 2022) for LINUX (help = h)
F6BVP-4 (Commands = ?) : u
Users - AX.25 Level 2 sessions :
Port Callsign Callsign AX.25 state ROSE state NetRom status
axudp F6BVP-5 -> F6BVP-9 Connected Connected ---------

Fixes: 3b3fd068c56e ("rose: Fix Null pointer dereference in rose_send_frame()")
Signed-off-by: Bernard Pidoux <f6bvp@free.fr>
Suggested-by: Francois Romieu <romieu@fr.zoreil.com>
Cc: Thomas DL9SAU Osterried <thomas@osterried.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/rose/rose_loopback.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/rose/rose_loopback.c b/net/rose/rose_loopback.c
index c318e5c9f6df3..56eea298b8ef7 100644
--- a/net/rose/rose_loopback.c
+++ b/net/rose/rose_loopback.c
@@ -99,7 +99,8 @@ static void rose_loopback_timer(struct timer_list *unused)
}

if (frametype == ROSE_CALL_REQUEST) {
- if (!rose_loopback_neigh->dev) {
+ if (!rose_loopback_neigh->dev &&
+ !rose_loopback_neigh->loopback) {
kfree_skb(skb);
continue;
}
--
2.35.1