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commit3b23a32a63upstream. 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(). We can not use seqlock here as it does not allow blocking. The writers already take RTNL anyway, so this does 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 on ioctl and rtnetlink paths. Note, bonding also changes slave mac addresses but that requires a separate patch due to the complexity of bonding code. Fixes:3710becf8a("net: RCU locking for simple ioctl()") Reported-by: "Gong, Sishuai" <sishuai@purdue.edu> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Cong Wang <cong.wang@bytedance.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.