From 0840556e5a3a331b6932ef17dd4bc94445df3297 Mon Sep 17 00:00:00 2001 From: Kuniyuki Iwashima Date: Mon, 29 Apr 2024 18:58:12 -0700 Subject: net: Protect dev->name by seqlock. 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 Link: https://lore.kernel.org/netdev/CANn89iJEWs7AYSJqGCUABeVqOCTkErponfZdT5kV-iD=-SajnQ@mail.gmail.com/ Signed-off-by: Kuniyuki Iwashima Link: https://lore.kernel.org/r/20240430015813.71143-7-kuniyu@amazon.com Signed-off-by: Jakub Kicinski --- include/linux/netdevice.h | 1 + net/core/dev.c | 27 +++++++++++++++++++++++---- 2 files changed, 24 insertions(+), 4 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index f849e7d110ed..41853424b41d 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -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, diff --git a/net/core/dev.c b/net/core/dev.c index cd7ba50eac15..e02d2363347e 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -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 @@ rollback: 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); -- cgit v1.2.3