Since commit c05cdb1b864f (netlink: allow large data transfers from
user-space), the kernel may fail to allocate the necessary room for the
acknowledgment message back to userspace. This patch introduces a new
socket option that trims off the payload of the original netlink message.
The netlink message header is still included, so the user can guess from
the sequence number what is the message that has triggered the
acknowledgment.
Cc: sta...@vger.kernel.org
Signed-off-by: Pablo Neira Ayuso pa...@netfilter.org
Signed-off-by: Christophe Ricard christophe-h.ric...@st.com
---
include/uapi/linux/netlink.h | 1 +
net/netlink/af_netlink.c | 27 ---
2 files changed, 25 insertions(+), 3 deletions(-)
diff --git a/include/uapi/linux/netlink.h b/include/uapi/linux/netlink.h
index cf6a65c..6f3fe16 100644
--- a/include/uapi/linux/netlink.h
+++ b/include/uapi/linux/netlink.h
@@ -110,6 +110,7 @@ struct nlmsgerr {
#define NETLINK_TX_RING7
#define NETLINK_LISTEN_ALL_NSID8
#define NETLINK_LIST_MEMBERSHIPS 9
+#define NETLINK_CAP_ACK10
struct nl_pktinfo {
__u32 group;
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 67d2104..131d1a4 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -84,6 +84,7 @@ struct listeners {
#define NETLINK_F_BROADCAST_SEND_ERROR 0x4
#define NETLINK_F_RECV_NO_ENOBUFS 0x8
#define NETLINK_F_LISTEN_ALL_NSID 0x10
+#define NETLINK_F_CAP_ACK 0x20
static inline int netlink_is_kernel(struct sock *sk)
{
@@ -2258,6 +2259,13 @@ static int netlink_setsockopt(struct socket *sock, int
level, int optname,
nlk-flags = ~NETLINK_F_LISTEN_ALL_NSID;
err = 0;
break;
+ case NETLINK_CAP_ACK:
+ if (val)
+ nlk-flags |= NETLINK_F_CAP_ACK;
+ else
+ nlk-flags = ~NETLINK_F_CAP_ACK;
+ err = 0;
+ break;
default:
err = -ENOPROTOOPT;
}
@@ -2332,6 +2340,16 @@ static int netlink_getsockopt(struct socket *sock, int
level, int optname,
netlink_table_ungrab();
break;
}
+ case NETLINK_CAP_ACK:
+ if (len sizeof(int))
+ return -EINVAL;
+ len = sizeof(int);
+ val = nlk-flags NETLINK_F_CAP_ACK ? 1 : 0;
+ if (put_user(len, optlen) ||
+ put_user(val, optval))
+ return -EFAULT;
+ err = 0;
+ break;
default:
err = -ENOPROTOOPT;
}
@@ -2873,9 +2891,12 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr
*nlh, int err)
struct nlmsghdr *rep;
struct nlmsgerr *errmsg;
size_t payload = sizeof(*errmsg);
+ struct netlink_sock *nlk = nlk_sk(NETLINK_CB(in_skb).sk);
- /* error messages get the original request appened */
- if (err)
+ /* Error messages get the original request appened, unless the user
+* requests to cap the error message.
+*/
+ if (!(nlk-flags NETLINK_F_CAP_ACK) err)
payload += nlmsg_len(nlh);
skb = netlink_alloc_skb(in_skb-sk, nlmsg_total_size(payload),
@@ -2898,7 +2919,7 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr
*nlh, int err)
NLMSG_ERROR, payload, 0);
errmsg = nlmsg_data(rep);
errmsg-error = err;
- memcpy(errmsg-msg, nlh, err ? nlh-nlmsg_len : sizeof(*nlh));
+ memcpy(errmsg-msg, nlh, payload sizeof(*errmsg) ? nlh-nlmsg_len :
sizeof(*nlh));
netlink_unicast(in_skb-sk, skb, NETLINK_CB(in_skb).portid,
MSG_DONTWAIT);
}
EXPORT_SYMBOL(netlink_ack);
--
2.1.4
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