On 06/16, Jay Vosburgh wrote: > Stanislav Fomichev <stfomichev@xxxxxxxxx> wrote: > > >On 06/16, Jay Vosburgh wrote: > >> Remove the ability to disable use_carrier in bonding, and remove > >> all code related to the old link state check that utilizes ethtool or > >> ioctl to determine the link state of an interface in a bond. > >> > >> To avoid acquiring RTNL many times per second, bonding's miimon > >> link monitor inspects link state under RCU, but not under RTNL. However, > >> ethtool implementations in drivers may sleep, and therefore the ethtool or > >> ioctl strategy is unsuitable for use with calls into driver ethtool > >> functions. > >> > >> The use_carrier option was introduced in 2003, to provide > >> backwards compatibility for network device drivers that did not support > >> the then-new netif_carrier_ok/on/off system. Today, device drivers are > >> expected to support netif_carrier_*, and the use_carrier backwards > >> compatibility logic is no longer necessary. > >> > >> Bonding now always behaves as if use_carrier=1, which relies on > >> netif_carrier_ok() to determine the link state of interfaces. This has > >> been the default setting for use_carrier since its introduction. For > >> backwards compatibility, the option itself remains, but may only be set to > >> 1, and queries will always return 1. > >> > >> Reported-by: syzbot+b8c48ea38ca27d150063@xxxxxxxxxxxxxxxxxxxxxxxxx > >> Closes: https://syzkaller.appspot.com/bug?extid=b8c48ea38ca27d150063 > >> Link: https://lore.kernel.org/lkml/000000000000eb54bf061cfd666a@xxxxxxxxxx/ > >> Link: https://lore.kernel.org/netdev/20240718122017.d2e33aaac43a.I10ab9c9ded97163aef4e4de10985cd8f7de60d28@changeid/ > >> Link: http://lore.kernel.org/netdev/aEt6LvBMwUMxmUyx@mini-arch > >> Signed-off-by: Jay Vosburgh <jv@xxxxxxxxxxxxx> > > > >Acked-by: Stanislav Fomichev <sdf@xxxxxxxxxxx> > > > >Maybe better to target 'net' with the following? > >Fixes: f7a11cba0ed7 ("bonding: hold ops lock around get_link") > > I targeted net-next and left the Fixes: tag off on purpose. > > First, the bug this nominally fixes is many years old, and > wasn't introduced by f7a11cba0ed7. > > More importantly, though, this patch is removing functionality > that someone theoretically could be relying on, and I don't think such > removals should happen in the middle of a stable series. The default > setting for use_carrier (i.e., using netif_carrier) will never hit the > issue in practice, so the exposure seems to be minimal for common use. SG, especially assuming that use_carrier has a default of 1 (so the issue should not appear in most/default setups).
