Re: [PATCH net] esp: do not unref managed frag pages in esp_ssg_unref()

[Steffen Klassert <steffen.klassert@secunet.com>]

On Sun, Jul 12, 2026 at 06:05:30PM +0100, Maher Azzouzi wrote:
> esp_ssg_unref() releases the page references held on the source
> scatterlist after the AEAD operation completes.  It calls
> skb_page_unref() on every frag page for an out-of-place transform
> (req->src != req->dst), and in the error path of esp_output_tail()
> (already_unref == true) on the request's own scatterlist.
> 
> This is wrong when the skb carries managed frags
> (SKBFL_MANAGED_FRAG_REFS).  Managed frags are owned by a zerocopy ubuf
> and the skb does not hold a per-frag page reference; io_uring SEND_ZC
> with a registered buffer attaches the bvec pages this way via
> io_sg_from_iter().  The rest of the stack honours this invariant:
> skb_release_data() skips the per-frag unref when SKBFL_MANAGED_FRAG_REFS
> is set, and skb_zcopy_managed() is the guard used at the other unref
> sites.
> 
> esp_ssg_unref() is missing that guard, so for a managed-frag skb it
> drops a page reference the skb never acquired.  This can underflow the
> page reference count and free a page that is still in use.
> 
> Guard the function with skb_zcopy_managed() so both unref paths are
> skipped for managed-frag skbs, matching skb_release_data().
> 
> Fixes: cac2661c53f3 ("esp4: Avoid skb_cow_data whenever possible")
> Fixes: 03e2a30f6a27 ("esp6: Avoid skb_cow_data whenever possible")
> Signed-off-by: Maher Azzouzi <maherazz04@gmail.com>

Applied to the ipsec tree, thanks a lot!