From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 606582E762C; Mon, 17 Aug 2026 15:12:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786979572; cv=none; b=FtTU5H6r48+fFTN3MD8OOzkuTbG1QIvEvuKiqP5R7EOer7guchdnCLNc5/5LGWOYVcY8MFjx//YISMEGJGP2e/Mmjbr4t+p2zFfHbGtOwJDH2Bq1BdpeUjnyDd0uz1NZ7uaWeaxiaK8rxABAg65EMl5ZRiz0fayQpHQIlxebdhk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786979572; c=relaxed/simple; bh=N5K4sqSjjiHb4Gm+162Xr1MTlOqWeoefwc6qXl8OEwg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=X4fNiBg6Sq8NASdPA9ovqGvP7v60P7lOrOtUIgiJuwkj62FacqKCJ6Ir+0u9+VKff2GbcRGSRggS/oHyTLSTLX12272d1SBQAq/tpKbvl7Hs/NR/g1X0cPto+joy6HneMV+uykgvTwFDUENplGO5PP0IYJ3h/RkXEsZg7p4AAOA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=UVllhP+/; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="UVllhP+/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B76451F000E9; Mon, 17 Aug 2026 15:12:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1786979571; bh=OfD5x5jV3QB0JqMjtRScn5snKwP8seUZUA2ycB0fZ9Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=UVllhP+/yO0shjZQ9wywNzrE/ipeLhivGx6V5NZXzy3J198GQr7oGSDYvBkFidIV0 DIiIXSJ7wdvbR2jE1f27bF9id5FDRqtBluGzH4ZYr/dyufH9NR47KsLScX798JN2pX Xk4aBsYIej9H+xt7QQZP7A3Jr0YBkbUV8ZRTTel4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, James Montgomery , Namjae Jeon , Steve French Subject: [PATCH 6.1 271/609] ksmbd: defer destroy_previous_session() until after NTLM authentication Date: Mon, 17 Aug 2026 15:29:27 +0200 Message-ID: <20260817132553.195141480@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260817132543.039278408@linuxfoundation.org> References: <20260817132543.039278408@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: James Montgomery commit c74801ee524f477c174a1899782b6c3b6918d407 upstream. In ntlm_authenticate(), destroy_previous_session() is called using a user pointer resolved from the client-supplied NTLM blob username field before the NTLMv2 response is validated. An authenticated attacker can set the NTLM blob username to match a victim account and set PreviousSessionId to the victim's session ID; destroy_previous_session() destroys the victim's session while ksmbd_decode_ntlmssp_auth_blob() subsequently rejects the request with -EPERM. Move destroy_previous_session() and the prev_id assignment to after ksmbd_decode_ntlmssp_auth_blob() returns success and use sess->user rather than the pre-authentication lookup result. This matches the ordering already used by krb5_authenticate(), where destroy_previous_session() is called only after ksmbd_krb5_authenticate() returns success. Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/linux-cifs/20260702155449.3639773-1-james_montgomery@disroot.org/ Signed-off-by: James Montgomery Acked-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman --- fs/smb/server/smb2pdu.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -1491,11 +1491,6 @@ static int ntlm_authenticate(struct ksmb return -EPERM; } - /* Check for previous session */ - prev_id = le64_to_cpu(req->PreviousSessionId); - if (prev_id && prev_id != sess->id) - destroy_previous_session(conn, user, prev_id); - if (sess->state == SMB2_SESSION_VALID) { /* * Reuse session if anonymous try to connect @@ -1533,6 +1528,10 @@ static int ntlm_authenticate(struct ksmb } } + prev_id = le64_to_cpu(req->PreviousSessionId); + if (prev_id && prev_id != sess->id) + destroy_previous_session(conn, sess->user, prev_id); + /* * If session state is SMB2_SESSION_VALID, We can assume * that it is reauthentication. And the user/password