Re: [PATCH net v2] macvlan: require init-userns CAP_NET_ADMIN to raise bc_queue_len

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <[email protected]>:

On Wed, 29 Jul 2026 20:06:21 +0000 you wrote:
> IFLA_MACVLAN_BC_QUEUE_LEN accepts any u32 and becomes
> port->bc_queue_len_used, the only bound on port->bc_queue. rtnetlink checks
> CAP_NET_ADMIN against the target netns only, so a user who unshares a
> user+net namespace, creates a veth and puts a macvlan on it can set the
> backlog to 0xffffffff and flood broadcast frames until the host dies:
> 
>   Out of memory: Killed process 141 (su) UID:0
>   Kernel panic - not syncing: System is deadlocked on memory
>   Call Trace:
>    vpanic (kernel/panic.c:650)
>    panic (kernel/panic.c:787)
>    out_of_memory (mm/oom_kill.c:1166)
>    __alloc_frozen_pages_noprof (mm/page_alloc.c:4914)
>    alloc_pages_mpol (mm/mempolicy.c:2490)
>    folio_alloc_noprof (mm/mempolicy.c:2591)
>    filemap_fault (mm/filemap.c:3565)
> 
> [...]

Here is the summary with links:
  - [net,v2] macvlan: require init-userns CAP_NET_ADMIN to raise bc_queue_len
    https://git.kernel.org/netdev/net-next/c/1a930d5734b7

You are awesome, thank you!
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