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net: trust the bitmap in __dev_alloc_name()

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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: Jiri Pirko <jiri@nvidia.com>
Link: https://lore.kernel.org/r/20231023152346.3639749-5-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski 2023-10-23 08:23:44 -07:00
parent 9a81046812
commit 7ad17b04dc
1 changed files with 4 additions and 11 deletions
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15
net/core/dev.c
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@ -1119,18 +1119,11 @@ static int __dev_alloc_name(struct net *net, const char *name, char *res)
i = find_first_zero_bit(inuse, max_netdevices); i = find_first_zero_bit(inuse, max_netdevices);
bitmap_free(inuse); bitmap_free(inuse);
if (i == max_netdevices)
return -ENFILE;
snprintf(buf, IFNAMSIZ, name, i); snprintf(res, IFNAMSIZ, name, i);
if (!netdev_name_in_use(net, buf)) { return i;
strscpy(res, buf, IFNAMSIZ);
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()) */ /* Returns negative errno or allocated unit id (see __dev_alloc_name()) */