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net: set initial device refcount to 1

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When adding CONFIG_PCPU_DEV_REFCNT, I forgot that the
initial net device refcount was 0.

When CONFIG_PCPU_DEV_REFCNT is not set, this means
the first dev_hold() triggers an illegal refcount
operation (addition on 0)

refcount_t: addition on 0; use-after-free.
WARNING: CPU: 0 PID: 1 at lib/refcount.c:25 refcount_warn_saturate+0x128/0x1a4

Fix is to change initial (and final) refcount to be 1.

Also add a missing kerneldoc piece, as reported by
Stephen Rothwell.

Fixes: 919067cc84 ("net: add CONFIG_PCPU_DEV_REFCNT")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Guenter Roeck <groeck@google.com>
Tested-by: Guenter Roeck <groeck@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2021-03-22 11:21:45 -07:00 committed by David S. Miller
parent 0ca99c84df
commit add2d73631
2 changed files with 7 additions and 3 deletions
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1
include/linux/netdevice.h
View File

@ -1792,6 +1792,7 @@ enum netdev_ml_priv_type {
*
* @proto_down_reason: reason a netdev interface is held down
* @pcpu_refcnt: Number of references to this device
* @dev_refcnt: Number of references to this device
* @todo_list: Delayed register/unregister
* @link_watch_list: XXX: need comments on this one
*

9
net/core/dev.c
View File

@ -10346,7 +10346,7 @@ static void netdev_wait_allrefs(struct net_device *dev)
rebroadcast_time = warning_time = jiffies;
refcnt = netdev_refcnt_read(dev);
while (refcnt != 0) {
while (refcnt != 1) {
if (time_after(jiffies, rebroadcast_time + 1 * HZ)) {
rtnl_lock();
@ -10383,7 +10383,7 @@ static void netdev_wait_allrefs(struct net_device *dev)
refcnt = netdev_refcnt_read(dev);
if (refcnt && time_after(jiffies, warning_time + 10 * HZ)) {
if (refcnt != 1 && time_after(jiffies, warning_time + 10 * HZ)) {
pr_emerg("unregister_netdevice: waiting for %s to become free. Usage count = %d\n",
dev->name, refcnt);
warning_time = jiffies;
@ -10459,7 +10459,7 @@ void netdev_run_todo(void)
netdev_wait_allrefs(dev);
/* paranoia */
BUG_ON(netdev_refcnt_read(dev));
BUG_ON(netdev_refcnt_read(dev) != 1);
BUG_ON(!list_empty(&dev->ptype_all));
BUG_ON(!list_empty(&dev->ptype_specific));
WARN_ON(rcu_access_pointer(dev->ip_ptr));
@ -10680,6 +10680,9 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
dev->pcpu_refcnt = alloc_percpu(int);
if (!dev->pcpu_refcnt)
goto free_dev;
dev_hold(dev);
#else
refcount_set(&dev->dev_refcnt, 1);
#endif
if (dev_addr_init(dev))