Re: [PATCH] mac802154: llsec: add skb_cow_data() before in-place crypto

From: Doruk Tan Ozturk <[email protected]>
Date: Mon, 25 May 2026 18:18:06 +0200

> [PATCH] mac802154: llsec: add skb_cow_data() before in-place crypto

Pls mark as "PATCH net".

> llsec_do_encrypt_unauth(), llsec_do_encrypt_auth(),
> llsec_do_decrypt_unauth(), and llsec_do_decrypt_auth() all perform
> in-place cryptographic transformations on skb data.  They build a
> scatterlist with sg_init_one() pointing into the skb's linear data area
> and then pass the same scatterlist as both src and dst to the crypto API
> (e.g. crypto_skcipher_encrypt/decrypt, crypto_aead_encrypt/decrypt).
> 
> On the RX path, __ieee802154_rx_handle_packet() clones the received skb
> before handing it to each subscriber via ieee802154_subif_frame().  The
> cloned skb shares the same underlying data buffer via reference
> counting.  When llsec_do_decrypt() subsequently modifies this shared
> buffer in place, it corrupts data that other clones -- potentially
> belonging to other sockets or subsystems -- still reference.
> 
> On the TX path, similar data sharing can occur when an skb's head has
> been cloned (skb_cloned() returns true).
> 
> The fix is to call skb_cow_data() before performing any in-place crypto
> operation.  skb_cow_data() ensures that the skb's data area is not
> shared: if the skb head is cloned or the data spans multiple fragments,
> it copies the data into a private buffer that can be safely modified in
> place.  This is the same pattern used by:
> 
>   - ESP (net/ipv4/esp4.c, net/ipv6/esp6.c)
>   - MACsec (drivers/net/macsec.c)
>   - WireGuard (drivers/net/wireguard/receive.c)
>   - TIPC (net/tipc/crypto.c)
> 
> Without this guard, in-place crypto on shared skb data leads to:
>   - Silent data corruption of other skb clones
>   - Use-after-free when the crypto API scatterwalk writes through a
>     page that has already been freed by another clone's kfree_skb()
>   - Kernel crashes under concurrent 802.15.4 traffic with security
>     enabled (KASAN/KMSAN reports slab-use-after-free)
> 
> This vulnerability was identified using 0sec.ai, an open-source
> automated security auditing platform (https://github.com/0sec-labs).
> 
> Fixes: 4c14a2fb5d14 ("mac802154: add llsec decryption method")
> Fixes: 03556e4d0dbb ("mac802154: add llsec encryption method")
> Cc: [email protected]
> Reported-by: Doruk Tan Ozturk <[email protected]>

Did you report this on LKML? If so, you should add

Closes: <link to your mail on lore>

right after the Reported-by.

> Signed-off-by: Doruk Tan Ozturk <[email protected]>
Other than that,

Reviewed-by: Alexander Lobakin <[email protected]>

Thanks,
Olek