From nobody Sat Feb 7 17:55:00 2026 Received: from mail-oo1-f69.google.com (mail-oo1-f69.google.com [209.85.161.69]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A3DEB2116F4 for ; Fri, 16 Jan 2026 12:51:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.161.69 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768567917; cv=none; b=Uu9sBeIIYZe9AVo2JiOvXu3Z39dY/96YhxqvX/VQNVr+bs0EPF5nN4Q82Uow2hkqkgaD5kZJ7hyFTriSUH8EoFxFoVyzP5S7W3Y9qogywrixXHqJCkbqoKqaa/YAREdqxJDbSD6JWRC7txN2CO+7FnMtRQSevkYye+FxjEtTYng= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768567917; c=relaxed/simple; bh=nPlTmiIxFUmaY4OEch1fp5e9o0QCnvWxq4IH5ShXqOU=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; b=lKB79y3YFQTjjAx92rtmxt60IdVYeAP0+bvr/9CmAcGnkSM899ffnnCgOfhIQ2oz5lHGVoFoeOYRcSfa34W8Nvv9DLt6X4dsR7oRNLWuEVJp7tQtlHJvSUp7ywO9wjiCJyQASnmp4HSn5dcrr+hr9J962Gw0CgzpPgmZlXPikYM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.161.69 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-oo1-f69.google.com with SMTP id 006d021491bc7-6610d8df861so3066535eaf.0 for ; Fri, 16 Jan 2026 04:51:55 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1768567914; x=1769172714; h=to:from:subject:message-id:in-reply-to:date:mime-version :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=NhfGWuamUiBczHpY4/COn3QPDbhId0eB3rDLvQAYzxg=; b=NkX+15cvzozSsBjOuiJuIu3SkrqH1sfCbwvMM/1/SLJmyki0VWQb4Z9Rt4dU+Lm2eV +Ivcw8tBnm95a/Kelo4GKVnthZtkdNaPXx0M7mkf1QrKkeIGSj4ptVYgN3i0ywxYN9lg xo8SmcCf9oZPdeP/H9a7q/Rm4Depzs2R8akXrlzuPexvd9lJ/OjS5zsPcxZKXwFg8az/ knuFa+ZGuzqBkjqHdC2lNj4zmG83wCslGaHyIYnXOSeV3mtqP2aJK6TMgPsiJUSfMPm4 GEovBgogJW/N0U1RjQA1bg4ZqgdcJKuLqQIFAbbd+b6QxpXAmFmxks0ES2kve8JkPIN6 mb2g== X-Gm-Message-State: AOJu0YyeNZChG1TKY8hrlDMZEdTWGGM7K6D7bI/+OSmarZUhjpCWRnHz xURixh3/dazm/wDHm7NaNCwqhtYST+uZhH9MRLau1D+k0HbnaaE06euiD7cBgjykJyAeGaXrEWw z+Ad3RAyNdQaV/nDf5vC3pW11VAKpbF8M7VYMgoTk+H0UgKmACmio3EIXA5E= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a4a:ba97:0:b0:661:1d0c:a5b3 with SMTP id 006d021491bc7-6611d0caaa0mr362942eaf.21.1768567914624; Fri, 16 Jan 2026 04:51:54 -0800 (PST) Date: Fri, 16 Jan 2026 04:51:54 -0800 In-Reply-To: <69694849.050a0220.58bed.0025.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <696a346a.050a0220.58bed.004a.GAE@google.com> Subject: Forwarded: [PATCH] netrom: fix memory leak in nr_add_node() From: syzbot To: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" For archival purposes, forwarding an incoming command email to linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com. *** Subject: [PATCH] netrom: fix memory leak in nr_add_node() Author: kartikey406@gmail.com #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git= master When nr_add_node() creates a new neighbor but the route quality is too low to be added (node already has 3 routes with better quality), the newly allocated neighbor is never used but remains in the neighbor list with refcount=3D1, causing a memory leak. Also fix the same leak in the error path when nr_node allocation fails after creating a new neighbor. Fix by tracking whether a new neighbor was allocated and removing it from the list if it was not used (count =3D=3D 0) or on allocation failure. Add debug printk to trace nr_rt_device_down cleanup. Reported-by: syzbot+3f2d46b6e62b8dd546d3@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3D3f2d46b6e62b8dd546d3 Signed-off-by: Deepanshu Kartikey --- net/netrom/af_netrom.c | 3 +++ net/netrom/nr_route.c | 39 ++++++++++++++++++++++++++++++++++++++- 2 files changed, 41 insertions(+), 1 deletion(-) diff --git a/net/netrom/af_netrom.c b/net/netrom/af_netrom.c index 5ed1a71ceec1..ecb47c8e2f0e 100644 --- a/net/netrom/af_netrom.c +++ b/net/netrom/af_netrom.c @@ -116,11 +116,14 @@ static int nr_device_event(struct notifier_block *thi= s, unsigned long event, voi { struct net_device *dev =3D netdev_notifier_info_to_dev(ptr); =20 + printk(KERN_ERR "nr_device_event: dev=3D%s event=3D%lu\n", dev->name, eve= nt); + if (!net_eq(dev_net(dev), &init_net)) return NOTIFY_DONE; =20 if (event !=3D NETDEV_DOWN) return NOTIFY_DONE; + printk(KERN_ERR "nr_device_event: calling nr_rt_device_down for %s\n", de= v->name); =20 nr_kill_by_device(dev); nr_rt_device_down(dev); diff --git a/net/netrom/nr_route.c b/net/netrom/nr_route.c index b94cb2ffbaf8..1fac8c6e5c26 100644 --- a/net/netrom/nr_route.c +++ b/net/netrom/nr_route.c @@ -100,11 +100,16 @@ static int __must_check nr_add_node(ax25_address *nr,= const char *mnemonic, { struct nr_node *nr_node; struct nr_neigh *nr_neigh; + bool new_neigh =3D false; int i, found; struct net_device *odev; =20 + printk(KERN_ERR "nr_add_node: entered, quality=3D%d\n", quality); + + if ((odev=3Dnr_dev_get(nr)) !=3D NULL) { /* Can't add routes to ourself */ dev_put(odev); + printk(KERN_ERR "nr_add_node: exit EINVAL (route to self)\n"); return -EINVAL; } =20 @@ -112,6 +117,8 @@ static int __must_check nr_add_node(ax25_address *nr, c= onst char *mnemonic, =20 nr_neigh =3D nr_neigh_get_dev(ax25, dev); =20 + printk(KERN_ERR "nr_add_node: nr_node=3D%p, nr_neigh=3D%p\n", nr_node, nr= _neigh); + /* * The L2 link to a neighbour has failed in the past * and now a frame comes from this neighbour. We assume @@ -172,6 +179,8 @@ static int __must_check nr_add_node(ax25_address *nr, c= onst char *mnemonic, } } =20 + new_neigh =3D true; + printk(KERN_ERR "nr_add_node: created new neighbor\n"); spin_lock_bh(&nr_neigh_list_lock); hlist_add_head(&nr_neigh->neigh_node, &nr_neigh_list); nr_neigh_hold(nr_neigh); @@ -182,9 +191,14 @@ static int __must_check nr_add_node(ax25_address *nr, = const char *mnemonic, nr_neigh->quality =3D quality; =20 if (nr_node =3D=3D NULL) { + printk(KERN_ERR "nr_add_node: creating new node\n"); if ((nr_node =3D kmalloc(sizeof(*nr_node), GFP_ATOMIC)) =3D=3D NULL) { - if (nr_neigh) + printk(KERN_ERR "nr_add_node: node alloc failed\n"); + if (nr_neigh) { + if (new_neigh) + nr_remove_neigh(nr_neigh); nr_neigh_put(nr_neigh); + } return -ENOMEM; } =20 @@ -209,6 +223,7 @@ static int __must_check nr_add_node(ax25_address *nr, c= onst char *mnemonic, spin_unlock_bh(&nr_node_list_lock); =20 nr_neigh_put(nr_neigh); + printk(KERN_ERR "nr_add_node: exit after new node, neigh count=3D%d\n", = nr_neigh->count); return 0; } nr_node_lock(nr_node); @@ -225,9 +240,12 @@ static int __must_check nr_add_node(ax25_address *nr, = const char *mnemonic, } } =20 + printk(KERN_ERR "nr_add_node: found=3D%d, nr_node->count=3D%d\n", found, = nr_node->count); + if (!found) { /* We have space at the bottom, slot it in */ if (nr_node->count < 3) { + printk(KERN_ERR "nr_add_node: adding route (count < 3)\n"); nr_node->routes[2] =3D nr_node->routes[1]; nr_node->routes[1] =3D nr_node->routes[0]; =20 @@ -242,6 +260,7 @@ static int __must_check nr_add_node(ax25_address *nr, c= onst char *mnemonic, } else { /* It must be better than the worst */ if (quality > nr_node->routes[2].quality) { + printk(KERN_ERR "nr_add_node: replacing worst route\n"); nr_node->routes[2].neighbour->count--; nr_neigh_put(nr_node->routes[2].neighbour); =20 @@ -255,6 +274,9 @@ static int __must_check nr_add_node(ax25_address *nr, c= onst char *mnemonic, nr_neigh_hold(nr_neigh); nr_neigh->count++; } + else { + printk(KERN_ERR "nr_add_node: quality too low, not adding\n"); + } } } =20 @@ -279,6 +301,15 @@ static int __must_check nr_add_node(ax25_address *nr, = const char *mnemonic, } } =20 + printk(KERN_ERR "nr_add_node: end, new_neigh=3D%d, count=3D%d\n", new_nei= gh, nr_neigh->count); + + if (new_neigh && nr_neigh->count =3D=3D 0) { + printk(KERN_ERR "nr_add_node: end, new_neigh=3D%d, count=3D%d\n", new_ne= igh, nr_neigh->count); + nr_remove_neigh(nr_neigh); + } else if (new_neigh) { + printk(KERN_ERR "nr_add_node: new_neigh used, count=3D%d\n", nr_neigh->c= ount); + } + nr_neigh_put(nr_neigh); nr_node_unlock(nr_node); nr_node_put(nr_node); @@ -511,14 +542,19 @@ void nr_rt_device_down(struct net_device *dev) struct nr_node *t; int i; =20 + printk(KERN_ERR "nr_rt_device_down: start for dev=3D%s (%p)\n", dev->name= , dev); + spin_lock_bh(&nr_neigh_list_lock); nr_neigh_for_each_safe(s, nodet, &nr_neigh_list) { + printk(KERN_ERR "nr_rt_device_down: checking neigh dev=3D%p vs %p\n", s-= >dev, dev); if (s->dev =3D=3D dev) { + printk(KERN_ERR "nr_rt_device_down: MATCH - removing neigh\n"); spin_lock_bh(&nr_node_list_lock); nr_node_for_each_safe(t, node2t, &nr_node_list) { nr_node_lock(t); for (i =3D 0; i < t->count; i++) { if (t->routes[i].neighbour =3D=3D s) { + printk(KERN_ERR "nr_rt_device_down: removing route %d\n", i); t->count--; =20 switch (i) { @@ -543,6 +579,7 @@ void nr_rt_device_down(struct net_device *dev) nr_remove_neigh_locked(s); } } + printk(KERN_ERR "nr_rt_device_down: done\n"); spin_unlock_bh(&nr_neigh_list_lock); } =20 --=20 2.43.0