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Merge branch 'net-deduplicate-netdev-name-allocation'

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Jakub Kicinski says:

====================
net: deduplicate netdev name allocation

After recent fixes we have even more duplicated code in netdev name
allocation helpers. There are two complications in this code.
First, __dev_alloc_name() clobbers its output arg even if allocation
fails, forcing callers to do extra copies. Second as our experience in
commit 55a5ec9b77 ("Revert "net: core: dev_get_valid_name is now the same as dev_alloc_name_ns"") and
commit 029b6d1405 ("Revert "net: core: maybe return -EEXIST in __dev_alloc_name"")
taught us, user space is very sensitive to the exact error codes.

Align the callers of __dev_alloc_name(), and remove some of its
complexity.

v1: https://lore.kernel.org/all/20231020011856.3244410-1-kuba@kernel.org/
====================

Link: https://lore.kernel.org/r/20231023152346.3639749-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski
2023-10-24 13:03:00 -07:00
parent fb1c535b13 ce4cfa2318
commit fcc017e3bc
1 changed files with 45 additions and 75 deletions
Download Patch File Download Diff File Expand all files Collapse all files
net/core/dev.c
+45 -75
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@@ -1057,7 +1057,7 @@ EXPORT_SYMBOL(dev_valid_name);
* __dev_alloc_name - allocate a name for a device
* @net: network namespace to allocate the device name in
* @name: name format string
* @buf: scratch buffer and result name string
* @res: result name string
*
* Passed a format string - eg "lt%d" it will try and find a suitable
* id. It scans list of devices to build up a free map, then chooses
@@ -1068,106 +1068,79 @@ EXPORT_SYMBOL(dev_valid_name);
* Returns the number of the unit assigned or a negative errno code.
*/
static int __dev_alloc_name(struct net *net, const char *name, char *buf)
static int __dev_alloc_name(struct net *net, const char *name, char *res)
{
int i = 0;
const char *p;
const int max_netdevices = 8*PAGE_SIZE;
unsigned long *inuse;
struct net_device *d;
char buf[IFNAMSIZ];
if (!dev_valid_name(name))
/* Verify the string as this thing may have come from the user.
* There must be one "%d" and no other "%" characters.
*/
p = strchr(name, '%');
if (!p || p[1] != 'd' || strchr(p + 2, '%'))
return -EINVAL;
p = strchr(name, '%');
if (p) {
/*
* Verify the string as this thing may have come from
* the user. There must be either one "%d" and no other "%"
* characters.
*/
if (p[1] != 'd' || strchr(p + 2, '%'))
return -EINVAL;
/* Use one page as a bit array of possible slots */
inuse = bitmap_zalloc(max_netdevices, GFP_ATOMIC);
if (!inuse)
return -ENOMEM;
/* Use one page as a bit array of possible slots */
inuse = bitmap_zalloc(max_netdevices, GFP_ATOMIC);
if (!inuse)
return -ENOMEM;
for_each_netdev(net, d) {
struct netdev_name_node *name_node;
for_each_netdev(net, d) {
struct netdev_name_node *name_node;
netdev_for_each_altname(d, name_node) {
if (!sscanf(name_node->name, name, &i))
continue;
if (i < 0 || i >= max_netdevices)
continue;
/* avoid cases where sscanf is not exact inverse of printf */
snprintf(buf, IFNAMSIZ, name, i);
if (!strncmp(buf, name_node->name, IFNAMSIZ))
__set_bit(i, inuse);
}
if (!sscanf(d->name, name, &i))
netdev_for_each_altname(d, name_node) {
if (!sscanf(name_node->name, name, &i))
continue;
if (i < 0 || i >= max_netdevices)
continue;
/* avoid cases where sscanf is not exact inverse of printf */
/* avoid cases where sscanf is not exact inverse of printf */
snprintf(buf, IFNAMSIZ, name, i);
if (!strncmp(buf, d->name, IFNAMSIZ))
if (!strncmp(buf, name_node->name, IFNAMSIZ))
__set_bit(i, inuse);
}
if (!sscanf(d->name, name, &i))
continue;
if (i < 0 || i >= max_netdevices)
continue;
i = find_first_zero_bit(inuse, max_netdevices);
bitmap_free(inuse);
/* avoid cases where sscanf is not exact inverse of printf */
snprintf(buf, IFNAMSIZ, name, i);
if (!strncmp(buf, d->name, IFNAMSIZ))
__set_bit(i, inuse);
}
snprintf(buf, IFNAMSIZ, name, i);
if (!netdev_name_in_use(net, buf))
return i;
i = find_first_zero_bit(inuse, max_netdevices);
bitmap_free(inuse);
if (i == max_netdevices)
return -ENFILE;
/* 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;
snprintf(res, IFNAMSIZ, name, i);
return i;
}
/* 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)
const char *want_name, char *out_name,
int dup_errno)
{
int ret;
if (!dev_valid_name(want_name))
return -EINVAL;
if (strchr(want_name, '%')) {
ret = __dev_alloc_name(net, want_name, out_name);
return ret < 0 ? ret : 0;
} else if (netdev_name_in_use(net, want_name)) {
return -EEXIST;
} else if (out_name != want_name) {
if (strchr(want_name, '%'))
return __dev_alloc_name(net, want_name, out_name);
if (netdev_name_in_use(net, want_name))
return -dup_errno;
if (out_name != want_name)
strscpy(out_name, want_name, IFNAMSIZ);
}
return 0;
}
static int dev_alloc_name_ns(struct net *net,
struct net_device *dev,
const char *name)
{
char buf[IFNAMSIZ];
int ret;
BUG_ON(!net);
ret = __dev_alloc_name(net, name, buf);
if (ret >= 0)
strscpy(dev->name, buf, IFNAMSIZ);
return ret;
}
/**
* dev_alloc_name - allocate a name for a device
* @dev: device
@@ -1184,20 +1157,17 @@ static int dev_alloc_name_ns(struct net *net,
int dev_alloc_name(struct net_device *dev, const char *name)
{
return dev_alloc_name_ns(dev_net(dev), dev, name);
return dev_prep_valid_name(dev_net(dev), dev, name, dev->name, ENFILE);
}
EXPORT_SYMBOL(dev_alloc_name);
static int dev_get_valid_name(struct net *net, struct net_device *dev,
const char *name)
{
char buf[IFNAMSIZ];
int ret;
ret = dev_prep_valid_name(net, dev, name, buf);
if (ret >= 0)
strscpy(dev->name, buf, IFNAMSIZ);
return ret;
ret = dev_prep_valid_name(net, dev, name, dev->name, EEXIST);
return ret < 0 ? ret : 0;
}
/**
@@ -11135,7 +11105,7 @@ int __dev_change_net_namespace(struct net_device *dev, struct net *net,
/* We get here if we can't use the current device name */
if (!pat)
goto out;
err = dev_prep_valid_name(net, dev, pat, new_name);
err = dev_prep_valid_name(net, dev, pat, new_name, EEXIST);
if (err < 0)
goto out;
}