netdev - [PATCH v1] net/handshake: Fix handshake_req_destroy

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Date: Tue, 06 Feb 2024 14:16:31 -0500
From: Chuck Lever <cel@...nel.org>
To: kernel-tls-handshake@...ts.linux.dev, netdev@...r.kernel.org
Cc: Chuck Lever <chuck.lever@...cle.com>
Subject: [PATCH v1] net/handshake: Fix handshake_req_destroy_test1

From: Chuck Lever <chuck.lever@...cle.com>

Recently, handshake_req_destroy_test1 started failing:

Expected handshake_req_destroy_test == req, but
    handshake_req_destroy_test == 0000000000000000
    req == 0000000060f99b40
not ok 11 req_destroy works

This is because "sock_release(sock)" was replaced with "fput(filp)"
to address a memory leak. Note that sock_release() is synchronous
but fput() usually delays the final close and clean-up.

The delay is not consequential in the other cases that were changed
but handshake_req_destroy_test1 is testing that handshake_req_cancel()
followed by closing the file actually does call the ->hp_destroy
method. Thus the PTR_EQ test at the end has to be sure that the
final close is complete before it checks the pointer.

We cannot use a completion here because if ->hp_destroy is never
called (ie, there is an API bug) then the test will hang.

Reported by: Guenter Roeck <linux@...ck-us.net>
Closes: https://lore.kernel.org/netdev/ZcKDd1to4MPANCrn@tissot.1015granger.net/T/#mac5c6299f86799f1c71776f3a07f9c566c7c3c40
Fixes: 4a0f07d71b04 ("net/handshake: Fix memory leak in __sock_create() and sock_alloc_file()")
Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
---
 net/handshake/handshake-test.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/handshake/handshake-test.c b/net/handshake/handshake-test.c
index 16ed7bfd29e4..34fd1d9b2db8 100644
--- a/net/handshake/handshake-test.c
+++ b/net/handshake/handshake-test.c
@@ -471,7 +471,10 @@ static void handshake_req_destroy_test1(struct kunit *test)
 	handshake_req_cancel(sock->sk);

 	/* Act */
-	fput(filp);
+	/* Ensure the close/release/put process has run to
+	 * completion before checking the result.
+	 */
+	__fput_sync(filp);

 	/* Assert */
 	KUNIT_EXPECT_PTR_EQ(test, handshake_req_destroy_test, req);