netdev - [PATCH v2 net-next] socket: Print pf->create() when it does not clear sock->sk on failure.

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Message-ID: <20241024201458.49412-1-kuniyu@amazon.com>
Date: Thu, 24 Oct 2024 13:14:58 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>
CC: Ignat Korchagin <ignat@...udflare.com>, Kuniyuki Iwashima
	<kuniyu@...zon.com>, Kuniyuki Iwashima <kuni1840@...il.com>,
	<netdev@...r.kernel.org>
Subject: [PATCH v2 net-next] socket: Print pf->create() when it does not clear sock->sk on failure.

I suggested to put DEBUG_NET_WARN_ON_ONCE() in __sock_create() to
catch possible use-after-free.

But the warning itself was not useful because our interest is in
the callee than the caller.

Let's define DEBUG_NET_WARN_ONCE() and print the name of pf->create()
and the socket identifier.

While at it, we enclose DEBUG_NET_WARN_ON_ONCE() in parentheses too
to avoid a checkpatch error.

Note that %pf or %pF were obsoleted and will be removed later as per
comment in lib/vsprintf.c.

Link: https://lore.kernel.org/netdev/202410231427.633734b3-lkp@intel.com/
Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
v2:
  * Use %ps instead of %pS as the offset is always zero

v1: https://lore.kernel.org/netdev/20241023191757.56735-1-kuniyu@amazon.com/
---
 include/net/net_debug.h | 4 +++-
 net/socket.c            | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/include/net/net_debug.h b/include/net/net_debug.h
index 1e74684cbbdb..9fecb1496be3 100644
--- a/include/net/net_debug.h
+++ b/include/net/net_debug.h
@@ -149,9 +149,11 @@ do {								\
 
 
 #if defined(CONFIG_DEBUG_NET)
-#define DEBUG_NET_WARN_ON_ONCE(cond) (void)WARN_ON_ONCE(cond)
+#define DEBUG_NET_WARN_ON_ONCE(cond) ((void)WARN_ON_ONCE(cond))
+#define DEBUG_NET_WARN_ONCE(cond, format...) ((void)WARN_ONCE(cond, format))
 #else
 #define DEBUG_NET_WARN_ON_ONCE(cond) BUILD_BUG_ON_INVALID(cond)
+#define DEBUG_NET_WARN_ONCE(cond, format...) BUILD_BUG_ON_INVALID(cond)
 #endif
 
 #endif	/* _LINUX_NET_DEBUG_H */
diff --git a/net/socket.c b/net/socket.c
index 9a8e4452b9b2..5fb3d265e492 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1578,7 +1578,9 @@ int __sock_create(struct net *net, int family, int type, int protocol,
 		/* ->create should release the allocated sock->sk object on error
 		 * and make sure sock->sk is set to NULL to avoid use-after-free
 		 */
-		DEBUG_NET_WARN_ON_ONCE(sock->sk);
+		DEBUG_NET_WARN_ONCE(sock->sk,
+				    "%ps must clear sock->sk on failure, family: %d, type: %d, protocol: %d\n",
+				    pf->create, family, type, protocol);
 		goto out_module_put;
 	}
 
-- 
2.39.5 (Apple Git-154)