| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <1308570046.4322.5.camel@jlt3.sipsolutions.net>
Date: Mon, 20 Jun 2011 13:40:46 +0200
From: Johannes Berg <johannes@...solutions.net>
To: netdev <netdev@...r.kernel.org>,
linux-wireless <linux-wireless@...r.kernel.org>
Cc: Samuel Ortiz <samuel@...tiz.org>,
"aloisio.almeida" <aloisio.almeida@...nbossa.org>,
John Linville <linville@...driver.com>,
Thomas Graf <tgraf@...g.ch>
Subject: [PATCH] netlink: advertise incomplete dumps
From: Johannes Berg <johannes.berg@...el.com>
Consider the following situation:
* a dump that would show 8 entries, four in the first
round, and four in the second
* between the first and second rounds, 6 entries are
removed
* now the second round will not show any entry, and
even if there is a sequence/generation counter the
application will not know
To solve this problem, add a new flag NLM_F_DUMP_INTR
to the netlink header that indicates the dump wasn't
consistent, this flag can also be set on the MSG_DONE
message that terminates the dump, and as such above
situation can be detected.
To achieve this, add a sequence counter to the netlink
callback struct. Of course, netlink code still needs
to use this new functionality. The correct way to do
that is to always set cb->seq when a dumpit callback
is invoked and call nl_dump_check_consistent() for
each new message. The core code will also call this
function for the final MSG_DONE message.
To make it usable with generic netlink, a new function
genlmsg_nlhdr() is needed to obtain the netlink header
from the genetlink user header.
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
---
Should we merge this through wireless? From wireless-next it'll go into
net-next quickly, but the converse isn't true, so using it in wireless
would be harder if it was merged through net-next I think? Or John can
cherry-pick into wireless-testing?
include/linux/netlink.h | 2 ++
include/net/genetlink.h | 32 ++++++++++++++++++++++++++++++++
include/net/netlink.h | 24 ++++++++++++++++++++++++
net/netlink/af_netlink.c | 2 ++
4 files changed, 60 insertions(+)
--- a/include/linux/netlink.h 2011-06-20 08:42:41.000000000 +0200
+++ b/include/linux/netlink.h 2011-06-20 09:39:19.000000000 +0200
@@ -49,6 +49,7 @@ struct nlmsghdr {
#define NLM_F_MULTI 2 /* Multipart message, terminated by NLMSG_DONE */
#define NLM_F_ACK 4 /* Reply with ack, with zero or error code */
#define NLM_F_ECHO 8 /* Echo this request */
+#define NLM_F_DUMP_INTR 16 /* Dump was inconsistent due to sequence change */
/* Modifiers to GET request */
#define NLM_F_ROOT 0x100 /* specify tree root */
@@ -222,6 +223,7 @@ struct netlink_callback {
struct netlink_callback *cb);
int (*done)(struct netlink_callback *cb);
int family;
+ unsigned int prev_seq, seq;
long args[6];
};
--- a/net/netlink/af_netlink.c 2011-06-20 08:42:41.000000000 +0200
+++ b/net/netlink/af_netlink.c 2011-06-20 09:39:19.000000000 +0200
@@ -1693,6 +1693,8 @@ static int netlink_dump(struct sock *sk)
if (!nlh)
goto errout_skb;
+ nl_dump_check_consistent(cb, nlh);
+
memcpy(nlmsg_data(nlh), &len, sizeof(len));
if (sk_filter(sk, skb))
--- a/include/net/genetlink.h 2011-06-20 08:42:41.000000000 +0200
+++ b/include/net/genetlink.h 2011-06-20 13:36:54.000000000 +0200
@@ -160,6 +160,38 @@ static inline void *genlmsg_put(struct s
}
/**
+ * genlmsg_nlhdr - Obtain netlink header from user specified header
+ * @user_hdr: user header as returned from genlmsg_put()
+ * @family: generic netlink family
+ *
+ * Returns pointer to netlink header.
+ */
+static inline struct nlmsghdr *genlmsg_nlhdr(void *user_hdr,
+ struct genl_family *family)
+{
+ return (struct nlmsghdr *)((char *)user_hdr -
+ family->hdrsize -
+ GENL_HDRLEN -
+ NLMSG_HDRLEN);
+}
+
+/**
+ * genl_dump_check_consistent - check if sequence is consistent and advertise if not
+ * @cb: netlink callback structure that stores the sequence number
+ * @user_hdr: user header as returned from genlmsg_put()
+ * @family: generic netlink family
+ *
+ * Cf. nl_dump_check_consistent(), this just provides a wrapper to make it
+ * simpler to use with generic netlink.
+ */
+static inline void genl_dump_check_consistent(struct netlink_callback *cb,
+ void *user_hdr,
+ struct genl_family *family)
+{
+ nl_dump_check_consistent(cb, genlmsg_nlhdr(user_hdr, family));
+}
+
+/**
* genlmsg_put_reply - Add generic netlink header to a reply message
* @skb: socket buffer holding the message
* @info: receiver info
--- a/include/net/netlink.h 2011-06-20 08:42:41.000000000 +0200
+++ b/include/net/netlink.h 2011-06-20 09:39:19.000000000 +0200
@@ -638,6 +638,30 @@ static inline int nlmsg_unicast(struct s
nlmsg_ok(pos, rem); \
pos = nlmsg_next(pos, &(rem)))
+/**
+ * nl_dump_check_consistent - check if sequence is consistent and advertise if not
+ * @cb: netlink callback structure that stores the sequence number
+ * @nlh: netlink message header to write the flag to
+ *
+ * This function checks if the sequence (generation) number changed during dump
+ * and if it did, advertises it in the netlink message header.
+ *
+ * The correct way to use it is to set cb->seq to the generation counter when
+ * all locks for dumping have been acquired, and then call this function for
+ * each message that is generated.
+ *
+ * Note that due to initialisation concerns, 0 is an invalid sequence number
+ * and must not be used by code that uses this functionality.
+ */
+static inline void
+nl_dump_check_consistent(struct netlink_callback *cb,
+ struct nlmsghdr *nlh)
+{
+ if (cb->prev_seq && cb->seq != cb->prev_seq)
+ nlh->nlmsg_flags |= NLM_F_DUMP_INTR;
+ cb->prev_seq = cb->seq;
+}
+
/**************************************************************************
* Netlink Attributes
**************************************************************************/
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Powered by blists - more mailing lists