Re: [PATCH net v5] ipv6: validate extension header length before copying to cmsg

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@xxxxxxxxxx>:

On Sat, 23 May 2026 22:32:45 +0800 you wrote:
> ip6_datagram_recv_specific_ctl() builds IPV6_{HOPOPTS,DSTOPTS,RTHDR}
> cmsgs (and their IPV6_2292* legacy counterparts) by trusting the
> on-wire hdrlen byte (ptr[1]) when computing the put_cmsg() length.
> The length was validated only at parse time (ipv6_parse_hopopts(),
> etc.).  An nftables payload-write expression can rewrite hdrlen after
> parsing and before the skb reaches recvmsg; the write itself is
> in-bounds but put_cmsg() then reads up to ((hdrlen+1) << 3) = 2040
> bytes from an 8-byte header.  nftables is reachable from an
> unprivileged user namespace, so this is an unprivileged
> slab-out-of-bounds read:
> 
> [...]

Here is the summary with links:
  - [net,v5] ipv6: validate extension header length before copying to cmsg
    https://git.kernel.org/netdev/net/c/dd433671fef3

You are awesome, thank you!
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