[PATCH 5.4 151/389] net: rose: fix netdev reference changes

Greg Kroah-Hartman
2022-08-23T11:27:45Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 931027820e4dafabc78aff82af59f8c1c4bd3128 ]

Bernard reported that trying to unload rose module would lead
to infamous messages:

unregistered_netdevice: waiting for rose0 to become free. Usage count = xx

This patch solves the issue, by making sure each socket referring to
a netdevice holds a reference count on it, and properly releases it
in rose_release().

rose_dev_first() is also fixed to take a device reference
before leaving the rcu_read_locked section.

Following patch will add ref_tracker annotations to ease
future bug hunting.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: Bernard Pidoux <f6bvp@free.fr>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Tested-by: Bernard Pidoux <f6bvp@free.fr>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/rose/af_rose.c | 11 +++++++++--
net/rose/rose_route.c | 2 ++
2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/net/rose/af_rose.c b/net/rose/af_rose.c
index 6a0df7c8a939..95dda29058a0 100644
--- a/net/rose/af_rose.c
+++ b/net/rose/af_rose.c
@@ -169,6 +169,7 @@ static void rose_kill_by_device(struct net_device *dev)
rose_disconnect(s, ENETUNREACH, ROSE_OUT_OF_ORDER, 0);
if (rose->neighbour)
rose->neighbour->use--;
+ dev_put(rose->device);
rose->device = NULL;
}
}
@@ -569,6 +570,8 @@ static struct sock *rose_make_new(struct sock *osk)
rose->idle = orose->idle;
rose->defer = orose->defer;
rose->device = orose->device;
+ if (rose->device)
+ dev_hold(rose->device);
rose->qbitincl = orose->qbitincl;

return sk;
@@ -622,6 +625,7 @@ static int rose_release(struct socket *sock)
break;
}

+ dev_put(rose->device);
sock->sk = NULL;
release_sock(sk);
sock_put(sk);
@@ -698,7 +702,6 @@ static int rose_connect(struct socket *sock, struct sockaddr *uaddr, int addr_le
struct rose_sock *rose = rose_sk(sk);
struct sockaddr_rose *addr = (struct sockaddr_rose *)uaddr;
unsigned char cause, diagnostic;
- struct net_device *dev;
ax25_uid_assoc *user;
int n, err = 0;

@@ -755,9 +758,12 @@ static int rose_connect(struct socket *sock, struct sockaddr *uaddr, int addr_le
}

if (sock_flag(sk, SOCK_ZAPPED)) { /* Must bind first - autobinding in this may or may not work */
+ struct net_device *dev;
+
sock_reset_flag(sk, SOCK_ZAPPED);

- if ((dev = rose_dev_first()) == NULL) {
+ dev = rose_dev_first();
+ if (!dev) {
err = -ENETUNREACH;
goto out_release;
}
@@ -765,6 +771,7 @@ static int rose_connect(struct socket *sock, struct sockaddr *uaddr, int addr_le
user = ax25_findbyuid(current_euid());
if (!user) {
err = -EINVAL;
+ dev_put(dev);
goto out_release;
}

diff --git a/net/rose/rose_route.c b/net/rose/rose_route.c
index 5f32113c9bbd..64d441d3b653 100644
--- a/net/rose/rose_route.c
+++ b/net/rose/rose_route.c
@@ -613,6 +613,8 @@ struct net_device *rose_dev_first(void)
if (first == NULL || strncmp(dev->name, first->name, 3) < 0)
first = dev;
}
+ if (first)
+ dev_hold(first);
rcu_read_unlock();

return first;
--
2.35.1