linux-kernel - Re: [syzbot] [hams?] KASAN: slab-use-after-free Read in nr_add

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <b5ontczz4n4gthaaeg6kfav3yaf25u4eax3uo46r44rcwap5hd@fpxvlsznasjp>
Date: Sun, 19 Oct 2025 10:40:03 +0530
From: Brahmajit Das <listout@...tout.xyz>
To: syzbot <syzbot+2860e75836a08b172755@...kaller.appspotmail.com>
Cc: davem@...emloft.net, edumazet@...gle.com, horms@...nel.org, 
	kuba@...nel.org, linux-hams@...r.kernel.org, linux-kernel@...r.kernel.org, 
	netdev@...r.kernel.org, pabeni@...hat.com, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [hams?] KASAN: slab-use-after-free Read in nr_add_node

On 18.10.2025 13:37, syzbot wrote:
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    f406055cb18c Merge tag 'arm64-fixes' of git://git.kernel.o..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=11cf767c580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=f3e7b5a3627a90dd
> dashboard link: https://syzkaller.appspot.com/bug?extid=2860e75836a08b172755
> compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=155f1de2580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12b6b52f980000
> 
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-f406055c.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/a4db2a99bfb1/vmlinux-f406055c.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/91d1ca420bac/bzImage-f406055c.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+2860e75836a08b172755@...kaller.appspotmail.com
> 
> ==================================================================
> BUG: KASAN: slab-use-after-free in nr_add_node+0x25db/0x2c00 net/netrom/nr_route.c:248
> Read of size 4 at addr ffff888054b8cc30 by task syz.3.7839/22393

#syz test linux-next

diff --git a/net/netrom/nr_route.c b/net/netrom/nr_route.c
index b94cb2ffbaf8..5fa7d9febbbb 100644
--- a/net/netrom/nr_route.c
+++ b/net/netrom/nr_route.c
@@ -245,7 +245,9 @@ static int __must_check nr_add_node(ax25_address *nr, const char *mnemonic,
 				nr_node->routes[2].neighbour->count--;
 				nr_neigh_put(nr_node->routes[2].neighbour);
 
-				if (nr_node->routes[2].neighbour->count == 0 && !nr_node->routes[2].neighbour->locked)
+				if (nr_node->routes[2].neighbour &&
+				    nr_node->routes[2].neighbour->count == 0 &&
+				    !nr_node->routes[2].neighbour->locked)
 					nr_remove_neigh(nr_node->routes[2].neighbour);
 
 				nr_node->routes[2].quality   = quality;

-- 
Regards,
listout