From: Kees Cook Date: Mon, 4 Mar 2024 21:29:31 +0000 (-0800) Subject: sock: Use unsafe_memcpy() for sock_copy() X-Git-Tag: block-6.9-20240315~27^2~101 X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=ff73f8344e58e7557819f92c88f289ffa6116be7;p=linux-block.git sock: Use unsafe_memcpy() for sock_copy() While testing for places where zero-sized destinations were still showing up in the kernel, sock_copy() and inet_reqsk_clone() were found, which are using very specific memcpy() offsets for both avoiding a portion of struct sock, and copying beyond the end of it (since struct sock is really just a common header before the protocol-specific allocation). Instead of trying to unravel this historical lack of container_of(), just switch to unsafe_memcpy(), since that's effectively what was happening already (memcpy() wasn't checking 0-sized destinations while the code base was being converted away from fake flexible arrays). Avoid the following false positive warning with future changes to CONFIG_FORTIFY_SOURCE: memcpy: detected field-spanning write (size 3068) of destination "&nsk->__sk_common.skc_dontcopy_end" at net/core/sock.c:2057 (size 0) Signed-off-by: Kees Cook Reviewed-by: Simon Horman Link: https://lore.kernel.org/r/20240304212928.make.772-kees@kernel.org Signed-off-by: Jakub Kicinski --- diff --git a/net/core/sock.c b/net/core/sock.c index df2ac54a8f74..43bf3818c19e 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -2053,8 +2053,9 @@ static void sock_copy(struct sock *nsk, const struct sock *osk) memcpy(nsk, osk, offsetof(struct sock, sk_dontcopy_begin)); - memcpy(&nsk->sk_dontcopy_end, &osk->sk_dontcopy_end, - prot->obj_size - offsetof(struct sock, sk_dontcopy_end)); + unsafe_memcpy(&nsk->sk_dontcopy_end, &osk->sk_dontcopy_end, + prot->obj_size - offsetof(struct sock, sk_dontcopy_end), + /* alloc is larger than struct, see sk_prot_alloc() */); #ifdef CONFIG_SECURITY_NETWORK nsk->sk_security = sptr; diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c index 747ed7344cbe..7d8090f109ef 100644 --- a/net/ipv4/inet_connection_sock.c +++ b/net/ipv4/inet_connection_sock.c @@ -906,8 +906,9 @@ static struct request_sock *inet_reqsk_clone(struct request_sock *req, memcpy(nreq_sk, req_sk, offsetof(struct sock, sk_dontcopy_begin)); - memcpy(&nreq_sk->sk_dontcopy_end, &req_sk->sk_dontcopy_end, - req->rsk_ops->obj_size - offsetof(struct sock, sk_dontcopy_end)); + unsafe_memcpy(&nreq_sk->sk_dontcopy_end, &req_sk->sk_dontcopy_end, + req->rsk_ops->obj_size - offsetof(struct sock, sk_dontcopy_end), + /* alloc is larger than struct, see above */); sk_node_init(&nreq_sk->sk_node); nreq_sk->sk_tx_queue_mapping = req_sk->sk_tx_queue_mapping;