On 4/27/20 1:29 PM, Jens Axboe wrote:
> On 4/27/20 1:20 PM, Jann Horn wrote:
>> On Sat, Apr 25, 2020 at 10:23 PM Jens Axboe <axboe@xxxxxxxxx> wrote:
>>> On 4/25/20 11:29 AM, Andreas Smas wrote:
>>>> Hi,
>>>>
>>>> Tried to use io_uring with OP_RECVMSG with ancillary buffers (for my
>>>> particular use case I'm using SO_TIMESTAMP for incoming UDP packets).
>>>>
>>>> These submissions fail with EINVAL due to the check in __sys_recvmsg_sock().
>>>>
>>>> The following hack fixes the problem for me and I get valid timestamps
>>>> back. Not suggesting this is the real fix as I'm not sure what the
>>>> implications of this is.
>>>>
>>>> Any insight into this would be much appreciated.
>>>
>>> It was originally disabled because of a security issue, but I do think
>>> it's safe to enable again.
>>>
>>> Adding the io-uring list and Jann as well, leaving patch intact below.
>>>
>>>> diff --git a/net/socket.c b/net/socket.c
>>>> index 2dd739fba866..689f41f4156e 100644
>>>> --- a/net/socket.c
>>>> +++ b/net/socket.c
>>>> @@ -2637,10 +2637,6 @@ long __sys_recvmsg_sock(struct socket *sock,
>>>> struct msghdr *msg,
>>>> struct user_msghdr __user *umsg,
>>>> struct sockaddr __user *uaddr, unsigned int flags)
>>>> {
>>>> - /* disallow ancillary data requests from this path */
>>>> - if (msg->msg_control || msg->msg_controllen)
>>>> - return -EINVAL;
>>>> -
>>>> return ____sys_recvmsg(sock, msg, umsg, uaddr, flags, 0);
>>>> }
>>
>> I think that's hard to get right. In particular, unix domain sockets
>> can currently pass file descriptors in control data - so you'd need to
>> set the file_table flag for recvmsg and sendmsg. And I'm not sure
>> whether, to make this robust, there should be a whitelist of types of
>> control messages that are permitted to be used with io_uring, or
>> something like that...
>>
>> I think of ancillary buffers as being kind of like ioctl handlers in
>> this regard.
>
> Good point. I'll send out something that hopefully will be enough to
> be useful, whole not allowing anything randomly.
That things is a bit of a mess... How about something like this for
starters?
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 084dfade5cda..40aa5b38367e 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3570,6 +3570,37 @@ static int io_sendmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
return ret;
}
+static bool __io_net_allow_cmsg(struct cmsghdr *cmsg)
+{
+ switch (cmsg->cmsg_level) {
+ case SOL_SOCKET:
+ if (cmsg->cmsg_type != SCM_RIGHTS &&
+ cmsg->cmsg_type != SCM_CREDENTIALS)
+ return true;
+ return false;
+ case SOL_IP:
+ case SOL_TCP:
+ case SOL_IPV6:
+ case SOL_ICMPV6:
+ case SOL_SCTP:
+ return true;
+ default:
+ return false;
+ }
+}
+
+static bool io_net_allow_cmsg(struct msghdr *msg)
+{
+ struct cmsghdr *cmsg;
+
+ for_each_cmsghdr(cmsg, msg) {
+ if (!__io_net_allow_cmsg(cmsg))
+ return false;
+ }
+
+ return true;
+}
+
static int io_sendmsg(struct io_kiocb *req, bool force_nonblock)
{
struct io_async_msghdr *kmsg = NULL;
@@ -3604,6 +3635,11 @@ static int io_sendmsg(struct io_kiocb *req, bool force_nonblock)
return ret;
}
+ if (!io_net_allow_cmsg(&kmsg->msg)) {
+ ret = -EINVAL;
+ goto err;
+ }
+
flags = req->sr_msg.msg_flags;
if (flags & MSG_DONTWAIT)
req->flags |= REQ_F_NOWAIT;
@@ -3617,6 +3653,7 @@ static int io_sendmsg(struct io_kiocb *req, bool force_nonblock)
ret = -EINTR;
}
+err:
if (kmsg && kmsg->iov != kmsg->fast_iov)
kfree(kmsg->iov);
req->flags &= ~REQ_F_NEED_CLEANUP;
@@ -3840,6 +3877,11 @@ static int io_recvmsg(struct io_kiocb *req, bool force_nonblock)
return ret;
}
+ if (!io_net_allow_cmsg(&kmsg->msg)) {
+ ret = -EINVAL;
+ goto err;
+ }
+
kbuf = io_recv_buffer_select(req, &cflags, !force_nonblock);
if (IS_ERR(kbuf)) {
return PTR_ERR(kbuf);
@@ -3863,6 +3905,7 @@ static int io_recvmsg(struct io_kiocb *req, bool force_nonblock)
ret = -EINTR;
}
+err:
if (kmsg && kmsg->iov != kmsg->fast_iov)
kfree(kmsg->iov);
req->flags &= ~REQ_F_NEED_CLEANUP;
diff --git a/net/socket.c b/net/socket.c
index 2dd739fba866..78cdf9a8cf73 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -2425,10 +2425,6 @@ static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
long __sys_sendmsg_sock(struct socket *sock, struct msghdr *msg,
unsigned int flags)
{
- /* disallow ancillary data requests from this path */
- if (msg->msg_control || msg->msg_controllen)
- return -EINVAL;
-
return ____sys_sendmsg(sock, msg, flags, NULL, 0);
}
@@ -2637,10 +2633,6 @@ long __sys_recvmsg_sock(struct socket *sock, struct msghdr *msg,
struct user_msghdr __user *umsg,
struct sockaddr __user *uaddr, unsigned int flags)
{
- /* disallow ancillary data requests from this path */
- if (msg->msg_control || msg->msg_controllen)
- return -EINVAL;
-
return ____sys_recvmsg(sock, msg, umsg, uaddr, flags, 0);
}
--
Jens Axboe
