From: David Yang <mmyangfl@gmail.com>
To: netdev@vger.kernel.org
Cc: David Yang <mmyangfl@gmail.com>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Simon Horman <horms@kernel.org>,
linux-kernel@vger.kernel.org
Subject: [PATCH net-next] net: netlink: warn on overwriting extack message
Date: Wed, 13 May 2026 22:32:16 +0800 [thread overview]
Message-ID: <20260513143219.3327287-1-mmyangfl@gmail.com> (raw)
When NL_SET_ERR_MSG is called more than once on the same extack, the
existing message is silently overwritten. This is hard to detect via
static analysis. Emit a rate-limited warning so these cases become
visible.
Signed-off-by: David Yang <mmyangfl@gmail.com>
---
include/linux/netlink.h | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index 882e9c1b6c1d..f6538304745f 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -90,6 +90,13 @@ struct netlink_ext_ack {
char _msg_buf[NETLINK_MAX_FMTMSG_LEN];
};
+#define __NL_SET_MSG(__extack, __msg) do { \
+ if (__extack->_msg) \
+ net_warn_ratelimited("overriding extack: %s", \
+ __extack->_msg); \
+ __extack->_msg = __msg; \
+} while (0)
+
/* Always use this macro, this allows later putting the
* message into a separate section or such for things
* like translation or listing all possible messages.
@@ -102,7 +109,7 @@ struct netlink_ext_ack {
do_trace_netlink_extack(__msg); \
\
if (__extack) \
- __extack->_msg = __msg; \
+ __NL_SET_MSG(__extack, __msg); \
} while (0)
/* We splice fmt with %s at each end even in the snprintf so that both calls
@@ -121,7 +128,7 @@ struct netlink_ext_ack {
\
do_trace_netlink_extack(__extack->_msg_buf); \
\
- __extack->_msg = __extack->_msg_buf; \
+ __NL_SET_MSG(__extack, __extack->_msg_buf); \
} while (0)
#define NL_SET_ERR_MSG_MOD(extack, msg) \
@@ -156,7 +163,7 @@ struct netlink_ext_ack {
do_trace_netlink_extack(__msg); \
\
if (__extack) { \
- __extack->_msg = __msg; \
+ __NL_SET_MSG(__extack, __msg); \
__extack->bad_attr = (attr); \
__extack->policy = (pol); \
} \
@@ -176,7 +183,7 @@ struct netlink_ext_ack {
\
do_trace_netlink_extack(__extack->_msg_buf); \
\
- __extack->_msg = __extack->_msg_buf; \
+ __NL_SET_MSG(__extack, __extack->_msg_buf); \
__extack->bad_attr = (attr); \
__extack->policy = (pol); \
} while (0)
--
2.53.0
reply other threads:[~2026-05-13 14:32 UTC|newest]
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