# Re: \[PATCH net v1 1/3\] net: core: propagate unreadable flag in skb\_zerocopy

- From: Pavel Begunkov \<asml.silence@gmail.com\>
- Date: 2026-08-02 12:33:13 
- List: netdev
- Page: https://ratatoskr.run/netdev/2026/08/17354298
- Thread: https://ratatoskr.run/netdev/2026/08/17352681/t.md

```text
On 8/1/26 13:52, Mina Almasry wrote:
> When skb_zerocopy() copies devmem payload fragments, it fails to update
> the target skb's unreadable flag. This causes the target to appear as
> readable memory.
>
> Propagate the unreadable flag if any devmem fragments were copied from
> the source.

From a quick look, it doesn't seem like the function would work reliably
with netmems even with this patch, but that's a different kind of issue
we can return to later. Curious, did you hit this in prod?

Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>

> Fixes: 65249feb6b3d ("net: add support for skbs with unreadable frags")
> Cc: Pavel Begunkov <asml.silence@gmail.com>
> Cc: Stanislav Fomichev <sdf@fomichev.me>
> Cc: Bobby Eshleman <redacted>
> Cc: Florian Westphal <fw@strlen.de>
> Signed-off-by: Mina Almasry <redacted>
> ---
>   net/core/skbuff.c | 3 +++
>   1 file changed, 3 insertions(+)
-- 
Pavel Begunkov

```