Re: [PATCH net v2] net: skbuff: fix pull-bound underflow in skb_checksum_setup_ipv6()

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski [off-list ref]:

On Sat, 19 Sep 2026 21:36:04 +0800 you wrote:

skb_maybe_pull_tail() subtracts skb_headlen(skb) from the unsigned max
argument and passes the result to __pskb_pull_tail() as a signed int.  The
function does not ensure that max is at least skb_headlen(skb).

This can happen while parsing IPv6 extension headers when an skb already
has a linear area larger than MAX_IPV6_HDR_LEN.  Once the parser needs data
beyond the linear area, max - skb_headlen(skb) wraps and is converted to a
negative delta.  __pskb_pull_tail() then passes that negative length to
skb_copy_bits(), where it can become a very large copy length.

[...]

Here is the summary with links:
  - [net,v2] net: skbuff: fix pull-bound underflow in skb_checksum_setup_ipv6()
    https://git.kernel.org/netdev/net/c/3b4e0b0c008a

You are awesome, thank you!
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