commit 86a7e0b69bd5b812e48a20c66c2161744f3caa16 upstream.
This commit was already queued for backport to 5.4+ but did not cleanly apply to 4.19 due to some merge conflicts. This patch fixes merge conflicts for backport to 4.19.
Callers of sock_sendmsg(), and similarly kernel_sendmsg(), in kernel space may observe their value of msg_name change in cases where BPF sendmsg hooks rewrite the send address. This has been confirmed to break NFS mounts running in UDP mode and has the potential to break other systems.
This patch:
1) Creates a new function called __sock_sendmsg() with same logic as the old sock_sendmsg() function. 2) Replaces calls to sock_sendmsg() made by __sys_sendto() and __sys_sendmsg() with __sock_sendmsg() to avoid an unnecessary copy, as these system calls are already protected. 3) Modifies sock_sendmsg() so that it makes a copy of msg_name if present before passing it down the stack to insulate callers from changes to the send address.
Link: https://lore.kernel.org/netdev/20230912013332.2048422-1-jrife@google.com/ Fixes: 1cedee13d25a ("bpf: Hooks for sys_sendmsg") Cc: stable@vger.kernel.org # 4.19.x Reviewed-by: Willem de Bruijn willemb@google.com Signed-off-by: Jordan Rife jrife@google.com Reviewed-by: Simon Horman horms@kernel.org Signed-off-by: David S. Miller davem@davemloft.net --- net/socket.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-)
diff --git a/net/socket.c b/net/socket.c index db9d908198f21..8c1a4e26c01fb 100644 --- a/net/socket.c +++ b/net/socket.c @@ -653,13 +653,30 @@ static inline int sock_sendmsg_nosec(struct socket *sock, struct msghdr *msg) return ret; }
-int sock_sendmsg(struct socket *sock, struct msghdr *msg) +static int __sock_sendmsg(struct socket *sock, struct msghdr *msg) { int err = security_socket_sendmsg(sock, msg, msg_data_left(msg));
return err ?: sock_sendmsg_nosec(sock, msg); } + +int sock_sendmsg(struct socket *sock, struct msghdr *msg) +{ + struct sockaddr_storage *save_addr = (struct sockaddr_storage *)msg->msg_name; + struct sockaddr_storage address; + int ret; + + if (msg->msg_name) { + memcpy(&address, msg->msg_name, msg->msg_namelen); + msg->msg_name = &address; + } + + ret = __sock_sendmsg(sock, msg); + msg->msg_name = save_addr; + + return ret; +} EXPORT_SYMBOL(sock_sendmsg);
/** @@ -963,7 +980,7 @@ static ssize_t sock_write_iter(struct kiocb *iocb, struct iov_iter *from) if (sock->type == SOCK_SEQPACKET) msg.msg_flags |= MSG_EOR;
- res = sock_sendmsg(sock, &msg); + res = __sock_sendmsg(sock, &msg); *from = msg.msg_iter; return res; } @@ -1896,7 +1913,7 @@ int __sys_sendto(int fd, void __user *buff, size_t len, unsigned int flags, if (sock->file->f_flags & O_NONBLOCK) flags |= MSG_DONTWAIT; msg.msg_flags = flags; - err = sock_sendmsg(sock, &msg); + err = __sock_sendmsg(sock, &msg);
out_put: fput_light(sock->file, fput_needed); @@ -2224,7 +2241,7 @@ static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg, err = sock_sendmsg_nosec(sock, msg_sys); goto out_freectl; } - err = sock_sendmsg(sock, msg_sys); + err = __sock_sendmsg(sock, msg_sys); /* * If this is sendmmsg() and sending to current destination address was * successful, remember it.