From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8EED52E3F1; Tue, 16 Jan 2024 00:24:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="W8WBtpDz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 30D0CC433C7; Tue, 16 Jan 2024 00:24:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1705364692; bh=JQAoC7EV7qWGl/rEHl8BcqZGhvjAK/8oXnEOwAcrnbg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=W8WBtpDzG66h3htQEqe3ShFvoGtDFuZ/VxtqhnqzGk+JmYkrqolV5cA//q6YyAx2k VK1tziwtWKZfTv06+B9H+gbd+ZU6q9rMtEOF26TADoZxTlalsqaUdyB8EbTsokMMKc fQg2hgPo72R+7RsH1Nsi68JKvTjU30YKkwrodBQAxp6aj3Z3a/vmPdIIUtuk/apiS1 A3isiGZwnmCxsw/sCqiaD8j7CQBLE6ddjw10cJhSb8UItJF9n6pp3MEJuuAxMKTADC RB9ZJnHnqFWS/vXkee5MG6J05PMiBs9VQFRG2DKfHyBYfDywllWeuKF0yzgEB532Q2 dp0r08M8H3GFg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Oleg Nesterov , David Howells , Marc Dionne , linux-afs@lists.infradead.org, Sasha Levin , davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, netdev@vger.kernel.org Subject: [PATCH AUTOSEL 6.6 17/19] rxrpc_find_service_conn_rcu: fix the usage of read_seqbegin_or_lock() Date: Mon, 15 Jan 2024 19:23:52 -0500 Message-ID: <20240116002413.215163-17-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240116002413.215163-1-sashal@kernel.org> References: <20240116002413.215163-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.6.12 Content-Transfer-Encoding: 8bit From: Oleg Nesterov [ Upstream commit bad1a11c0f061aa073bab785389fe04f19ba02e1 ] rxrpc_find_service_conn_rcu() should make the "seq" counter odd on the second pass, otherwise read_seqbegin_or_lock() never takes the lock. Signed-off-by: Oleg Nesterov Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org Link: https://lore.kernel.org/r/20231117164846.GA10410@redhat.com/ Signed-off-by: Sasha Levin --- net/rxrpc/conn_service.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/rxrpc/conn_service.c b/net/rxrpc/conn_service.c index 89ac05a711a4..39c908a3ca6e 100644 --- a/net/rxrpc/conn_service.c +++ b/net/rxrpc/conn_service.c @@ -25,7 +25,7 @@ struct rxrpc_connection *rxrpc_find_service_conn_rcu(struct rxrpc_peer *peer, struct rxrpc_conn_proto k; struct rxrpc_skb_priv *sp = rxrpc_skb(skb); struct rb_node *p; - unsigned int seq = 0; + unsigned int seq = 1; k.epoch = sp->hdr.epoch; k.cid = sp->hdr.cid & RXRPC_CIDMASK; @@ -35,6 +35,7 @@ struct rxrpc_connection *rxrpc_find_service_conn_rcu(struct rxrpc_peer *peer, * under just the RCU read lock, so we have to check for * changes. */ + seq++; /* 2 on the 1st/lockless path, otherwise odd */ read_seqbegin_or_lock(&peer->service_conn_lock, &seq); p = rcu_dereference_raw(peer->service_conns.rb_node); -- 2.43.0