| Message ID | 20240216232220.it.450-kees@kernel.org (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v2] sock: Use unsafe_memcpy() for sock_copy() | expand |
From: Kees Cook <keescook@chromium.org> Date: Fri, 16 Feb 2024 15:22:23 -0800 > 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 <keescook@chromium.org> > --- > Cc: Jakub Kicinski <kuba@kernel.org> > Cc: "David S. Miller" <davem@davemloft.net> > Cc: Eric Dumazet <edumazet@google.com> > Cc: Paolo Abeni <pabeni@redhat.com> > Cc: netdev@vger.kernel.org > > v2- add inet_reqsk_clone() instance too > v1- https://lore.kernel.org/lkml/20240216204423.work.066-kees@kernel.org/ > --- > net/core/sock.c | 5 +++-- > net/ipv4/inet_connection_sock.c | 5 +++-- > 2 files changed, 6 insertions(+), 4 deletions(-) > > diff --git a/net/core/sock.c b/net/core/sock.c > index 0a7f46c37f0c..b7ea358eb18f 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 459af1f89739..4a1d96ba3ad1 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 sk_prot_alloc() */); nit: reqsk is allocated in inet_reqsk_clone(). > > sk_node_init(&nreq_sk->sk_node); > nreq_sk->sk_tx_queue_mapping = req_sk->sk_tx_queue_mapping; > -- > 2.34.1 >
diff --git a/net/core/sock.c b/net/core/sock.c index 0a7f46c37f0c..b7ea358eb18f 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 459af1f89739..4a1d96ba3ad1 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 sk_prot_alloc() */); sk_node_init(&nreq_sk->sk_node); nreq_sk->sk_tx_queue_mapping = req_sk->sk_tx_queue_mapping;
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 <keescook@chromium.org> --- Cc: Jakub Kicinski <kuba@kernel.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: Eric Dumazet <edumazet@google.com> Cc: Paolo Abeni <pabeni@redhat.com> Cc: netdev@vger.kernel.org v2- add inet_reqsk_clone() instance too v1- https://lore.kernel.org/lkml/20240216204423.work.066-kees@kernel.org/ --- net/core/sock.c | 5 +++-- net/ipv4/inet_connection_sock.c | 5 +++-- 2 files changed, 6 insertions(+), 4 deletions(-)