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can: isotp: support MSG_TRUNC flag when reading from socket

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When providing the MSG_TRUNC flag via recvmsg() syscall the return value
provides the real length of the packet or datagram, even when it was longer
than the passed buffer.

Fixes: e057dd3fc2 ("can: add ISO 15765-2:2016 transport protocol")
Link: https://github.com/linux-can/can-utils/issues/347#issuecomment-1065932671
Link: https://lore.kernel.org/all/20220316164258.54155-3-socketcan@hartkopp.net
Suggested-by: Derek Will <derekrobertwill@gmail.com>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
This commit is contained in:
Oliver Hartkopp 2022-03-16 17:42:58 +01:00 committed by Marc Kleine-Budde
parent 30ffd5332e
commit 42bf50a179
1 changed files with 15 additions and 12 deletions
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27
net/can/isotp.c
View File

@ -1047,29 +1047,28 @@ static int isotp_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
struct sock *sk = sock->sk; struct sock *sk = sock->sk;
struct sk_buff *skb; struct sk_buff *skb;
struct isotp_sock *so = isotp_sk(sk); struct isotp_sock *so = isotp_sk(sk);
int err = 0; int noblock = flags & MSG_DONTWAIT;
int noblock; int ret = 0;
noblock = flags & MSG_DONTWAIT; if (flags & ~(MSG_DONTWAIT | MSG_TRUNC))
flags &= ~MSG_DONTWAIT; return -EINVAL;
if (!so->bound) if (!so->bound)
return -EADDRNOTAVAIL; return -EADDRNOTAVAIL;
skb = skb_recv_datagram(sk, flags, noblock, &err); flags &= ~MSG_DONTWAIT;
skb = skb_recv_datagram(sk, flags, noblock, &ret);
if (!skb) if (!skb)
return err; return ret;
if (size < skb->len) if (size < skb->len)
msg->msg_flags |= MSG_TRUNC; msg->msg_flags |= MSG_TRUNC;
else else
size = skb->len; size = skb->len;
err = memcpy_to_msg(msg, skb->data, size); ret = memcpy_to_msg(msg, skb->data, size);
if (err < 0) { if (ret < 0)
skb_free_datagram(sk, skb); goto out_err;
return err;
}
sock_recv_timestamp(msg, sk, skb); sock_recv_timestamp(msg, sk, skb);
@ -1079,9 +1078,13 @@ static int isotp_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
memcpy(msg->msg_name, skb->cb, msg->msg_namelen); memcpy(msg->msg_name, skb->cb, msg->msg_namelen);
} }
/* set length of return value */
ret = (flags & MSG_TRUNC) ? skb->len : size;
out_err:
skb_free_datagram(sk, skb); skb_free_datagram(sk, skb);
return size; return ret;
} }
static int isotp_release(struct socket *sock) static int isotp_release(struct socket *sock)