Commit bddc0921 authored by Weiming Shi's avatar Weiming Shi Committed by Jakub Kicinski
Browse files

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: 3b23a32a ("net: fix dev_ifsioc_locked() race condition")
Reported-by: default avatarXiang Mei <xmei5@asu.edu>
Signed-off-by: default avatarWeiming Shi <bestswngs@gmail.com>
Reviewed-by: default avatarWillem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20260520075736.3415676-3-bestswngs@gmail.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 2bccfb84

drivers/net/tap.c

+1 −1
Original line number Diff line number Diff line
@@ -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;