From d8b6529e80bcb4fb8177121404cbb3377acaebd2 Mon Sep 17 00:00:00 2001 From: Zijie Huang Date: Mon, 21 Sep 2026 01:36:19 +0800 Subject: [PATCH] net: arp: terminate device name before lookup The ARP ioctl copies a user-provided struct arpreq into a stack object. Its arp_dev field may contain IFNAMSIZ bytes without a NUL terminator. Such input is passed to dev_get_by_name_rcu() or __dev_get_by_name(), where strcmp() can read past the end of the stack object when a matching alternative interface name exists. Terminate the field before the lookup to prevent the out-of-bounds read. Fixes: 36fbf1e52bd3 ("net: rtnetlink: add linkprop commands to add and delete alternative ifnames") Cc: stable@vger.kernel.org Reported-by: Vega Signed-off-by: Zijie Huang Signed-off-by: Ren Wei Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/fabf02a70787d17299e4b3153eadffaf20d154b3.1789910973.git.milkory@outlook.com Signed-off-by: Jakub Kicinski --- net/ipv4/arp.c | 1 + 1 file changed, 1 insertion(+) diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c index d409f606aec0..60009d92e071 100644 --- a/net/ipv4/arp.c +++ b/net/ipv4/arp.c @@ -1278,6 +1278,7 @@ int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg) err = copy_from_user(&r, arg, sizeof(struct arpreq)); if (err) return -EFAULT; + r.arp_dev[IFNAMSIZ - 1] = '\0'; break; default: return -EINVAL;