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Sun, 19 Oct 2025 06:55:17 -0700 (PDT) Date: Sun, 19 Oct 2025 06:55:17 -0700 In-Reply-To: <68d56f4d.050a0220.25d7ab.0047.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <68f4edc5.050a0220.1be48.0001.GAE@google.com> Subject: Forwarded: Re: [syzbot] [hams?] KASAN: slab-use-after-free Read 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: Re: [syzbot] [hams?] KASAN: slab-use-after-free Read in nr_add_node Author: listout@listout.xyz On 18.10.2025 13:37, syzbot wrote: > syzbot has found a reproducer for the following issue on: >=20 > 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=3D11cf767c580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=3Df3e7b5a3627a9= 0dd > dashboard link: https://syzkaller.appspot.com/bug?extid=3D2860e75836a08b1= 72755 > compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binuti= ls for Debian) 2.40 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=3D155f1de2580= 000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=3D12b6b52f980000 >=20 > Downloadable assets: > disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d= 900f083ada3/non_bootable_disk-f406055c.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/a4db2a99bfb1/vmlinu= x-f406055c.xz > kernel image: https://storage.googleapis.com/syzbot-assets/91d1ca420bac/b= zImage-f406055c.xz >=20 > IMPORTANT: if you fix the issue, please add the following tag to the comm= it: > Reported-by: syzbot+2860e75836a08b172755@syzkaller.appspotmail.com >=20 > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > BUG: KASAN: slab-use-after-free in nr_add_node+0x25db/0x2c00 net/netrom/n= r_route.c:248 > Read of size 4 at addr ffff888054b8cc30 by task syz.3.7839/22393 #syz test linux-next 1c64efcb083c48c85227cb4d72ab137feef2cdac diff --git a/net/netrom/nr_route.c b/net/netrom/nr_route.c index b94cb2ffbaf8..aa72c4db2be4 100644 --- a/net/netrom/nr_route.c +++ b/net/netrom/nr_route.c @@ -242,11 +242,12 @@ static int __must_check nr_add_node(ax25_address *nr,= const char *mnemonic, } else { /* It must be better than the worst */ if (quality > nr_node->routes[2].quality) { - nr_node->routes[2].neighbour->count--; - nr_neigh_put(nr_node->routes[2].neighbour); + struct nr_neigh *old_neighbour =3D nr_node->routes[2].neighbour; + old_neighbour->count--; + nr_neigh_put(old_neighbour); =20 - if (nr_node->routes[2].neighbour->count =3D=3D 0 && !nr_node->routes[2= ].neighbour->locked) - nr_remove_neigh(nr_node->routes[2].neighbour); + if (old_neighbour->count =3D=3D 0 && !old_neighbour->locked) + nr_remove_neigh(old_neighbour); =20 nr_node->routes[2].quality =3D quality; nr_node->routes[2].obs_count =3D obs_count; --=20 Regards, listout