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 9D935526A96 for ; Mon, 7 Sep 2026 20:00:24 +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=1788811225; cv=none; b=ljTCxg5T3KQrCSR6H0A5PjIF8hvL7JkhmaCMKOvX6UsXdM9xD0v+4TgXqqXiJDjSRwBC5PiqJNUCpFM3CFiHutkpy75vmDQQ1PbK4O5UcnMPvr1HC/YhAE6INGC78Ko5UjY6pGxq/jv6r1sxigPADnFyteg0Fhsa83mxVFksk1c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788811225; c=relaxed/simple; bh=E2xdLiKqaFWt8bFhlE1xPHszk592SqyouTCmZI9OCPA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=d6gGl5AY1WEooCScAhnPxUDI5ToYaUhcMxMWXT645o6PsoshxfXVFA015w1RtpvbDmmJji/MXETQOC1FsYsFDaPYVX8O5jYqVni9hbfpET3r+i7VSv6/IfyKfCFq+5sKoXxJQEptJKTktghJ3fDvd1XAEdetvHo6XMytTVrd5s4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GW9ch3US; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="GW9ch3US" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C14BA1F00A3F; Mon, 7 Sep 2026 20:00:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788811224; bh=bGxEjeszGSXFaq/NFJE2nmr6S7ZDUhq92M/F2L0Xz2w=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=GW9ch3USErw9iDHh9cBZ+Vh9h/uvCAK5dDiObMfHOC5E+w74y2Fj0I/cjuEsb+LDF 7MfUyJjgvIJugJoRQqFYOxCf5OPG1uHTu2RetPB4naqaiKzR+o1JT2wRgNjKMm/MU9 XcsbTtZcmW6KquqTDkIwdSeYXixruZQU1lki++9Yfne1QdyehxBhqHXpXTYpzcGtB6 3WHFvU8ddV5K9s2Y4QkeGkSVqKYEFA+tVh5oticGPmPFgA2sjVHbZsKgUIglv9ruvl A4FewngRxm/eyHu6YmPRCeeizIDqyY5jWblhHujmG0sw24tGrYnmA4T4SI3pXM4Rn5 SsJiHkKWhZMpQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Frank Sorenson , Namjae Jeon , Paulo Alcantara , Sasha Levin Subject: [PATCH 6.6.y 4/4] smb: client: fix UAF and buffer leak in cifs_check_trans2() for malformed secondary T2 Date: Mon, 7 Sep 2026 16:00:18 -0400 Message-ID: <20260907200018.326904-4-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260907200018.326904-1-sashal@kernel.org> References: <2026090303-fiddling-giant-6389@gregkh> <20260907200018.326904-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Frank Sorenson [ Upstream commit 730d0bb19507b9e19c2fe5343109ac618e2fbce5 ] When a valid primary TRANSACT2 response has been received (mid->resp_buf set, mid->multiRsp true) and a subsequent secondary response causes cifs_check_trans2() to return false -- either because the SMB header is invalid (malformed != 0) or because check2ndT2() rejects the PDU -- handle_mid() overwrites mid->resp_buf with the new buffer (leaking the primary buffer) and, because mid->multiRsp is set, skips the server->smallbuf/bigbuf NULL-out. When the user thread frees mid->resp_buf, server->smallbuf or server->bigbuf is left dangling; the demux thread reuses it for the next packet, resulting in a use-after-free. Combine both early-exit conditions and, when mid->multiRsp is already set, abort the pending transaction inline: set multiEnd, call dequeue_mid() with malformed=true, and return true so handle_mid() exits without touching mid->resp_buf or the server buffer pointers. Fixes: 316cf94a910f ("CIFS: Move trans2 processing to ops struct") Cc: stable@vger.kernel.org # cifs_check_trans2() is in smb1ops.c on kernels < 7.0 Signed-off-by: Frank Sorenson Signed-off-by: Namjae Jeon Signed-off-by: Paulo Alcantara Signed-off-by: Sasha Levin --- fs/smb/client/smb1transport.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/fs/smb/client/smb1transport.c b/fs/smb/client/smb1transport.c index 824604cb0e468..de240840d59ff 100644 --- a/fs/smb/client/smb1transport.c +++ b/fs/smb/client/smb1transport.c @@ -386,10 +386,18 @@ static bool cifs_check_trans2(struct mid_q_entry *mid, struct TCP_Server_Info *server, char *buf, int malformed) { - if (malformed) - return false; - if (check2ndT2(buf) <= 0) + if (malformed || check2ndT2(buf) <= 0) { + /* mid->multiRsp blocks the server buf detach in handle_mid(); + * returning false here would leak resp_buf and leave a dangling + * server->smallbuf/bigbuf after the user thread frees resp_buf. + */ + if (mid->multiRsp) { + mid->multiEnd = true; + dequeue_mid(server, mid, true); + return true; + } return false; + } mid->multiRsp = true; if (mid->resp_buf) { /* merge response - fix up 1st*/ -- 2.53.0