Messages in this thread | ![/](/images/icornerl.gif) | | From | Siddh Raman Pant <> | Subject | [PATCH net-next v5 0/2] nfc: Fix UAF during datagram sending caused by missing refcounting | Date | Wed, 13 Dec 2023 00:19:18 +0530 |
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Changes in v5: - Move reason = LLCP_DM_REJ under the fail_put_sock label. - Checkpatch now warns about == NULL check for new_sk, so fix that, and also at other similar places in the same function.
Changes in v4: - Fix put ordering and comments. - Separate freeing in recv() into end labels. - Remove obvious comment and add reasoning. - Picked up r-bs by Suman.
Changes in v3: - Fix missing freeing statements.
Changes in v2: - Add net-next in patch subject. - Removed unnecessary extra lock and hold nfc_dev ref when holding llcp_sock. - Remove last formatting patch. - Picked up r-b from Krzysztof for LLCP_BOUND patch.
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For connectionless transmission, llcp_sock_sendmsg() codepath will eventually call nfc_alloc_send_skb() which takes in an nfc_dev as an argument for calculating the total size for skb allocation.
virtual_ncidev_close() codepath eventually releases socket by calling nfc_llcp_socket_release() (which sets the sk->sk_state to LLCP_CLOSED) and afterwards the nfc_dev will be eventually freed.
When an ndev gets freed, llcp_sock_sendmsg() will result in an use-after-free as it
(1) doesn't have any checks in place for avoiding the datagram sending.
(2) calls nfc_llcp_send_ui_frame(), which also has a do-while loop which can race with freeing. This loop contains the call to nfc_alloc_send_skb() where we dereference the nfc_dev pointer.
nfc_dev is being freed because we do not hold a reference to it when we hold a reference to llcp_local. Thus, virtual_ncidev_close() eventually calls nfc_release() due to refcount going to 0.
Since state has to be LLCP_BOUND for datagram sending, we can bail out early in llcp_sock_sendmsg().
Please review and let me know if any errors are there, and hopefully this gets accepted.
Thanks, Siddh
Siddh Raman Pant (2): nfc: llcp_core: Hold a ref to llcp_local->dev when holding a ref to llcp_local nfc: Do not send datagram if socket state isn't LLCP_BOUND
net/nfc/llcp_core.c | 72 +++++++++++++++++++++++++++++---------------- net/nfc/llcp_sock.c | 5 ++++ 2 files changed, 52 insertions(+), 25 deletions(-)
-- 2.42.0
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