On Sat, 30 Jan 2021 18:27:55 -0800 Cong Wang wrote:
> From: Cong Wang <[email protected]>
>
> dev_ifsioc_locked() is called with only RCU read lock, so when
> there is a parallel writer changing the mac address, it could
> get a partially updated mac address, as shown below:
>
> Thread 1 Thread 2
> // eth_commit_mac_addr_change()
> memcpy(dev->dev_addr, addr->sa_data, ETH_ALEN);
> // dev_ifsioc_locked()
> memcpy(ifr->ifr_hwaddr.sa_data,
> dev->dev_addr,...);
>
> Close this race condition by guarding them with a RW semaphore,
> like netdev_get_name(). The writers take RTNL anyway, so this
> will not affect the slow path. To avoid bothering existing
> dev_set_mac_address() callers in drivers, introduce a new wrapper
> just for user-facing callers in ioctl and rtnetlink.
Some of the drivers need to be update, tho, right? At a quick look at
least bond and tun seem to be making calls to dev_set_mac_address()
on IOCTL paths.
> Fixes: 3710becf8a58 ("net: RCU locking for simple ioctl()")
> Reported-by: "Gong, Sishuai" <[email protected]>
> Cc: Eric Dumazet <[email protected]>
> Cc: Jakub Kicinski <[email protected]>
> Signed-off-by: Cong Wang <[email protected]>
> ---
> include/linux/netdevice.h | 3 +++
> net/core/dev.c | 40 +++++++++++++++++++++++++++++++++++++++
> net/core/dev_ioctl.c | 20 +++++++-------------
> net/core/rtnetlink.c | 2 +-
> 4 files changed, 51 insertions(+), 14 deletions(-)
