From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793723978; b=zww6llB5VSY/uSiHOLZgNzn5seGNzCLMZrzcQ1E7Xgb0ZDkFdq4fCqUMWwv4IRTl3lp/ T6RGVlPYUFnZvEaWdxmwMrnG6imMuFbkfyJ76kCGVspp7nqP2MpLg9IBjPtPJaaNjLaWq SQVqOJIPpDrXWXVdd03y1qKtNP/LQ48qXlWwWG/stZBizWcuzzc66yGueJfZNdjsu+VES EzTBMWOhu3YBnP+Gv8inmpx6tXQTq5ETTrDtkhkfvaf57/SWe7pf6/TiiasoH/T/z56Fe lZJPhmbYeV2b+VeluI5Sm3WuZDq8LMDwX4qmNp446pHpSIkJZCJmUVlaNHHRC+Rw7Bg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793723978; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=91QgwEfxl8W1kdK4arIilG24I1a6A7OWOfpadQ42GFw=; b=UDncc8yRssnRgVizlUrmKRcA3TFgPpNRI9EwNR49OJNlLX3rnMuGQYa8io2gRS+mKsT1 AH0R67p6cjBhXRqjPKDZRDUQiIJnBvAKf7vAAxoTEiebADqFyt2pWANtkgL0Fa8mB6AN7 JssnwGKj36R4lPuiLkNT7NwjUCwwpbiK0rjMLHzEz11nGN9nKUtALq9E7llJK1R+a2hJf cxHXYOgyBZb0G7ngrsezYJOgnwcYmhsZTrCOFEZfj7g2Oc4wl/MnWoaUKhihAXm/FNoY7 cpNIarpj3rkEPZ0e3WP+8PRzAyefKoqz8wEM38jmpCL0fmlBaIREId95bcXwczyRjww== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b="f2OeKI/m"; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2F20E60A6F47 for ; Tue, 3 Nov 2026 16:39:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=f2OeKI/m Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8BE031F0093A; Tue, 3 Nov 2026 16:39:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793723978; bh=91QgwEfxl8W1kdK4arIilG24I1a6A7OWOfpadQ42GFw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=f2OeKI/m4nggdcp50FvYvUnqeH5S+COAMRn5+bQ2Kop3fxVOf9K7Ee8cfcXHbx8P2 k6wYspqC8zed+tTkdqI4BbrnWd+/WfkCDQuWpCa4NNNkQqOlbWH+SMelLqpwNCGor0 HFN0F/XeTb8NnkEKDmxNGIZ6ftw5XcNW7IjoN3ItIsImn37IbAk2PsqRHvolxJQwxy D3ZH/XBmr7u2tCU8dWEVH0JtMMCYeUVMoVyjwJcpyK7U7Bt2cJlqSunDSysxLBHvXX eRxTQ0z6kFICvGTXvYpXBcUPHjW0cNIETa1N7yCtDGkFpmaK15dvTZFWOd7qPbLNVR EVcFEjQqqGavA== From: Sasha Levin To: stable@vger.kernel.org Cc: Ian Bridges , Namjae Jeon , Sasha Levin Subject: [PATCH 6.12.y] ksmbd: fix session reference leak on compounded SESSION_SETUP Date: Tue, 3 Nov 2026 11:39:36 -0500 Message-ID: <20261103163910.472406-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026110318-mountain-transpire-6844@gregkh> References: <2026110318-mountain-transpire-6844@gregkh> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Ian Bridges [ Upstream commit 03bd8f5279e490e15e0c0f0fa388ffbd2fbacd65 ] A compound request can place SESSION_SETUP after another command. That earlier command leaves a reference to its session in work->sess. smb2_sess_setup() then overwrites work->sess with the session it looks up or creates, and the dispatcher later puts work->sess only once. The inherited reference is never dropped. That leaks the session, together with its setup connection and socket, and every repeat of the compound leaks another. unreferenced object (size 512): __kmalloc_cache_noprof+0x32c/0x3a0 ksmbd_smb2_session_create+0xf6/0x9c0 [ksmbd] smb2_sess_setup+0xda4/0x6280 [ksmbd] handle_ksmbd_work+0x88c/0x1cb0 [ksmbd] Save the inherited session on entry. After the request has been processed, release it once, but only when smb2_sess_setup() has replaced work->sess with its own session or cleared it. Do this after ksmbd_conn_unlock() so the put does not run under srv_mutex. An error path may instead leave the inherited session in work->sess. Keep it there, so the dispatcher still puts it and the error response is still signed or encrypted with it as before. Fixes: 7aa8804c0b67 ("ksmbd: fix user-after-free from session log off") Cc: stable@vger.kernel.org Signed-off-by: Ian Bridges Signed-off-by: Namjae Jeon [ sashal: omitted the installed flag update for the absent early work->sess assignment ] Signed-off-by: Sasha Levin --- fs/smb/server/smb2pdu.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c index 5f752434be3cf..ef851d5c605b4 100644 --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -1707,6 +1707,8 @@ int smb2_sess_setup(struct ksmbd_work *work) struct smb2_sess_setup_req *req; struct smb2_sess_setup_rsp *rsp; struct ksmbd_session *sess; + struct ksmbd_session *prev_sess = work->sess; + bool installed = false; struct negotiate_message *negblob; unsigned int negblob_len, negblob_off; int rc = 0; @@ -1844,6 +1846,7 @@ int smb2_sess_setup(struct ksmbd_work *work) conn->binding = false; } work->sess = sess; + installed = true; negblob_off = le16_to_cpu(req->SecurityBufferOffset); negblob_len = le16_to_cpu(req->SecurityBufferLength); @@ -1997,6 +2000,14 @@ int smb2_sess_setup(struct ksmbd_work *work) } ksmbd_conn_unlock(conn); + + /* + * Later in a compound, work->sess holds the reference that an + * earlier command took. Drop it once this request has installed + * its own session there or cleared it. + */ + if (prev_sess && (installed || !work->sess)) + ksmbd_user_session_put(prev_sess); return rc; } -- 2.53.0