Re: [PATCH net 1/2] macsec: set IFF_UNICAST_FLT priv flag

[Stanislav Fomichev <stfomichev@gmail.com>]

On 07/22, Simon Horman wrote:
> On Mon, Jul 21, 2025 at 09:54:22AM -0700, Stanislav Fomichev wrote:
> > Cosmin reports the following locking issue:
> > 
> >   # BUG: sleeping function called from invalid context at
> >   kernel/locking/mutex.c:275
> >   #   dump_stack_lvl+0x4f/0x60
> >   #   __might_resched+0xeb/0x140
> >   #   mutex_lock+0x1a/0x40
> >   #   dev_set_promiscuity+0x26/0x90
> >   #   __dev_set_promiscuity+0x85/0x170
> >   #   __dev_set_rx_mode+0x69/0xa0
> >   #   dev_uc_add+0x6d/0x80
> >   #   vlan_dev_open+0x5f/0x120 [8021q]
> >   #  __dev_open+0x10c/0x2a0
> >   #  __dev_change_flags+0x1a4/0x210
> >   #  netif_change_flags+0x22/0x60
> >   #  do_setlink.isra.0+0xdb0/0x10f0
> >   #  rtnl_newlink+0x797/0xb00
> >   #  rtnetlink_rcv_msg+0x1cb/0x3f0
> >   #  netlink_rcv_skb+0x53/0x100
> >   #  netlink_unicast+0x273/0x3b0
> >   #  netlink_sendmsg+0x1f2/0x430
> > 
> > Which is similar to recent syzkaller reports in [0] and [1] and triggers
> > because macsec does not advertise IFF_UNICAST_FLT although it has proper
> > ndo_set_rx_mode callback that takes care of pushing uc/mc addresses
> > down to the real device.
> > 
> > In general, dev_uc_add call path is problematic for stacking
> > non-IFF_UNICAST_FLT because we might grab netdev instance lock under
> > addr_list_lock spinlock, so this is not a systemic fix.
> > 
> > 0: https://lore.kernel.org/netdev/686d55b4.050a0220.1ffab7.0014.GAE@google.com
> > 1: https://lore.kernel.org/netdev/68712acf.a00a0220.26a83e.0051.GAE@google.com/
> > Link: 2aff4342b0f5b1539c02ffd8df4c7e58dd9746e7.camel@nvidia.com
> 
> I think that Link: should be followed by a URL
> 
> Link: https://lore.kernel.org/netdev/2aff4342b0f5b1539c02ffd8df4c7e58dd9746e7.camel@nvidia.com

Whoops, sorry, forgot to prefix the message id with a URL :-( If this
gets a CR, I'll repost with a fix. (presumably should be easy to fix
during git am)
 
> > Fixes: 7e4d784f5810 ("net: hold netdev instance lock during rtnetlink operations")
> > Reported-by: Cosmin Ratiu <cratiu@nvidia.com>
> > Tested-by: Cosmin Ratiu <cratiu@nvidia.com>
> > Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
> 
> Hi Stan,
> 
> I ran the test provided by patch 2/2.
> When run with with a debug kernel using VNG.
> 
> It reliably passes with patch 1/2 applied. And fails without patch 1/2 applied.
> Where fails means the kernel panics along the lines of the stack trace in
> the commit message.
> 
> Reviewed-by: Simon Horman <horms@kernel.org>
> Tested-by: Simon Horman <horms@kernel.org>

Thank you for testing!