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net: Protect dev->name by seqlock.

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We will convert ioctl(SIOCGARP) to RCU, and then we need to copy
dev->name which is currently protected by rtnl_lock().

This patch does the following:

  1) Add seqlock netdev_rename_lock to protect dev->name

  2) Add netdev_copy_name() that copies dev->name to buffer
     under netdev_rename_lock

  3) Use netdev_copy_name() in netdev_get_name() and drop
     devnet_rename_sem

Suggested-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/netdev/CANn89iJEWs7AYSJqGCUABeVqOCTkErponfZdT5kV-iD=-SajnQ@mail.gmail.com/
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20240430015813.71143-7-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Kuniyuki Iwashima 2024-04-29 18:58:12 -07:00 committed by Jakub Kicinski
parent a428bfc77a
commit 0840556e5a
2 changed files with 24 additions and 4 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

1
include/linux/netdevice.h
View file

@ -3136,6 +3136,7 @@ struct net_device *netdev_get_by_name(struct net *net, const char *name,
netdevice_tracker *tracker, gfp_t gfp);
struct net_device *dev_get_by_index_rcu(struct net *net, int ifindex);
struct net_device *dev_get_by_napi_id(unsigned int napi_id);
void netdev_copy_name(struct net_device *dev, char *name);
static inline int dev_hard_header(struct sk_buff *skb, struct net_device *dev,
unsigned short type,

27
net/core/dev.c
View file

@ -940,6 +940,18 @@ struct net_device *dev_get_by_napi_id(unsigned int napi_id)
}
EXPORT_SYMBOL(dev_get_by_napi_id);
static DEFINE_SEQLOCK(netdev_rename_lock);
void netdev_copy_name(struct net_device *dev, char *name)
{
unsigned int seq;
do {
seq = read_seqbegin(&netdev_rename_lock);
strscpy(name, dev->name, IFNAMSIZ);
} while (read_seqretry(&netdev_rename_lock, seq));
}
/**
* netdev_get_name - get a netdevice name, knowing its ifindex.
* @net: network namespace
@ -951,7 +963,6 @@ int netdev_get_name(struct net *net, char *name, int ifindex)
struct net_device *dev;
int ret;
down_read(&devnet_rename_sem);
rcu_read_lock();
dev = dev_get_by_index_rcu(net, ifindex);
@ -960,12 +971,11 @@ int netdev_get_name(struct net *net, char *name, int ifindex)
goto out;
}
strcpy(name, dev->name);
netdev_copy_name(dev, name);
ret = 0;
out:
rcu_read_unlock();
up_read(&devnet_rename_sem);
return ret;
}
@ -1217,7 +1227,10 @@ int dev_change_name(struct net_device *dev, const char *newname)
memcpy(oldname, dev->name, IFNAMSIZ);
write_seqlock(&netdev_rename_lock);
err = dev_get_valid_name(net, dev, newname);
write_sequnlock(&netdev_rename_lock);
if (err < 0) {
up_write(&devnet_rename_sem);
return err;
@ -1257,7 +1270,9 @@ int dev_change_name(struct net_device *dev, const char *newname)
if (err >= 0) {
err = ret;
down_write(&devnet_rename_sem);
write_seqlock(&netdev_rename_lock);
memcpy(dev->name, oldname, IFNAMSIZ);
write_sequnlock(&netdev_rename_lock);
memcpy(oldname, newname, IFNAMSIZ);
WRITE_ONCE(dev->name_assign_type, old_assign_type);
old_assign_type = NET_NAME_RENAMED;
@ -11403,8 +11418,12 @@ int __dev_change_net_namespace(struct net_device *dev, struct net *net,
dev_net_set(dev, net);
dev->ifindex = new_ifindex;
if (new_name[0]) /* Rename the netdev to prepared name */
if (new_name[0]) {
/* Rename the netdev to prepared name */
write_seqlock(&netdev_rename_lock);
strscpy(dev->name, new_name, IFNAMSIZ);
write_sequnlock(&netdev_rename_lock);
}
/* Fixup kobjects */
dev_set_uevent_suppress(&dev->dev, 1);