Commit 7ad17b04 authored by Jakub Kicinski's avatar Jakub Kicinski
Browse files

net: trust the bitmap in __dev_alloc_name() 



Prior to restructuring __dev_alloc_name() handled both printf
and non-printf names. In a clever attempt at code reuse it
always prints the name into a buffer and checks if it's
a duplicate.

Trust the bitmap, and return an error if its full.

This shrinks the possible ID space by one from 32K to 32K - 1,
as previously the max value would have been tried as a valid ID.
It seems very unlikely that anyone would care as we heard
no requests to increase the max beyond 32k.

Reviewed-by: default avatarJiri Pirko <jiri@nvidia.com>
Link: https://lore.kernel.org/r/20231023152346.3639749-5-kuba@kernel.org


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 9a810468

net/core/dev.c

+4 −11
Original line number Diff line number Diff line
@@ -1119,20 +1119,13 @@ static int __dev_alloc_name(struct net *net, const char *name, char *res) 


	i = find_first_zero_bit(inuse, max_netdevices);

	bitmap_free(inuse);

	if (i == max_netdevices)

		return -ENFILE;



	snprintf(buf, IFNAMSIZ, name, i);

	if (!netdev_name_in_use(net, buf)) {

		strscpy(res, buf, IFNAMSIZ);

	snprintf(res, IFNAMSIZ, name, i);

	return i;

}



	/* It is possible to run out of possible slots

	 * when the name is long and there isn't enough space left

	 * for the digits, or if all bits are used.

	 */

	return -ENFILE;

}



/* Returns negative errno or allocated unit id (see __dev_alloc_name()) */

static int dev_prep_valid_name(struct net *net, struct net_device *dev,

			       const char *want_name, char *out_name,