From bddc09212c24934643bd44fc794748d2bbb3b6cd Mon Sep 17 00:00:00 2001 From: Weiming Shi Date: Wed, 20 May 2026 00:57:38 -0700 Subject: [PATCH] tap: fix stack info leak in tap_ioctl() SIOCGIFHWADDR In the SIOCGIFHWADDR path, tap_ioctl() copies 16 bytes of an uninitialised on-stack struct sockaddr_storage to userspace via ifr_hwaddr, but netif_get_mac_address() only writes sa_family and dev->addr_len (6 for Ethernet) bytes, leaving sa_data[6..13] uninitialised. Those 8 trailing bytes leak kernel stack contents; SIOCGIFHWADDR on a macvtap chardev returns kernel .text and direct-map pointers, defeating KASLR. Initialise ss at declaration. Fixes: 3b23a32a6321 ("net: fix dev_ifsioc_locked() race condition") Reported-by: Xiang Mei Signed-off-by: Weiming Shi Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20260520075736.3415676-3-bestswngs@gmail.com Signed-off-by: Jakub Kicinski --- drivers/net/tap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/tap.c b/drivers/net/tap.c index b8240737dc51..a590e07ce0a9 100644 --- a/drivers/net/tap.c +++ b/drivers/net/tap.c @@ -919,11 +919,11 @@ static long tap_ioctl(struct file *file, unsigned int cmd, struct tap_queue *q = file->private_data; struct tap_dev *tap; void __user *argp = (void __user *)arg; + struct sockaddr_storage ss = {}; struct ifreq __user *ifr = argp; unsigned int __user *up = argp; unsigned short u; int __user *sp = argp; - struct sockaddr_storage ss; int s; int ret;