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=1793745598; b=OB57VahxXWccF+UQnTXg1eKNRbYScRZgvfiDIOFf4OXdTYNzkD1oy+vmwvNIIKmtORcP o/NiNl8yiaY8zh8m72Fr56lmDyz9Py4OLU1Pm0Z8w9xDkP0DCDNmEwXQB0tdy09EzdPvm U7hPZQXO2n06K8kokvBUZmam1bDy3ZQxwLtsOg3X8Jlw31TApXmbOV4iGkrtSyy4wSwVo vAg49vBsiXfZStKBcCjYPHfDx57VHSoX2mLuHqIXaU7vhB+YpK5P1pLmCfGD6I0HaSVwb w75pDd0q6jIj5LvchATeKkqyCzUyD/21Uv11x0VFSXYP2ZKWvBAzUkW0giY0cOrHxIQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793745598; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=xQtCebo7YacYA/pqqCBx5V6g1CGUMugwEAbYp3/9NDg=; b=VVOggj+15I3MyxQCiMzQub32GDcEV26fFLNofXcWYZL5WIgyUwyyqk/pPv/oR1qKCW4T xgmozrTtmX2kp+5vaoccoyPg4ax4uxrNO/GXPcMWz4YeGJBTjmVad+Xej4dUGOvValoqH 8dqIyYJivJ8LBh/InamHQWBV1gbDTbSMJoIiDiKFpKz8i8NrY7EwtnX2CRqW1SpsZRvEc yFPItu7io4qimKGvbOb25nKQ6vokWr15l4WhZccdcsJlbgMd9zpqPT1GxNsuCW5TM0URe 3ikN5nCDWBlM39X3UjZD29znX420lfiy9MeB2s2+ivml7Vui+R2GVMfukjGokcO9Udg== 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=YRQzkIDl; 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 EF211606A33E for ; Tue, 3 Nov 2026 22:39:57 +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=YRQzkIDl Received: by smtp.kernel.org (Postfix) with ESMTPSA id 56BE91F00919; Tue, 3 Nov 2026 22:39:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793745597; bh=xQtCebo7YacYA/pqqCBx5V6g1CGUMugwEAbYp3/9NDg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=YRQzkIDlSaFkkCW7rjW7D4jlRlyb0nPQyOcorrhEVo5P7wYpMWyuF+4rQYNybPiMJ vzhbn5HO/+XyKNctLCwZ+vlEzQL+X2BiB2FeuOXnAB4bGVQPX2/cJl2venb807pBNA 2Bg0fBFK0s/fXhJoEEsa3DcSSGYdy0Ovg9pmrnt58HZUtIqIU3PJf1URCIbLYRbL7t hLbPNJLvbC1mP/ptp+SBFSAc+D2zJENlnr0BK+6lKR4SE0fmkBDTvO2BVyD8YLjP+Q X2tduogaB0J4JDg6wDT9WXYfoUPgOFAq130hkE+cBD1R40f+/8QFbBefSTf9mh6kKE JFCUXlz0AS+ng== From: Sasha Levin To: stable@vger.kernel.org Cc: Ian Bridges , Namjae Jeon , Sasha Levin Subject: [PATCH 6.6.y] ksmbd: fix out-of-bounds read when padding the final compound response Date: Tue, 3 Nov 2026 17:39:56 -0500 Message-ID: <20261103223845.1550564-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026110341-crispness-repave-e347@gregkh> References: <2026110341-crispness-repave-e347@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 714f27729121d59f103ca4dad7b0c2d1c125cd71 ] Compound response handling pads the last response of a compound to an 8-byte boundary by growing the final iov and the RFC1002 length. smb2_allocate_rsp_buf() allocates exactly response_sz. A command can fill the response buffer to within 7 bytes of its end, for example a QUERY_INFO whose output is bounded only by the space left. The padding can then run past the allocation, and ksmbd_tcp_writev() reads those bytes when it sends the response. BUG: KASAN: slab-out-of-bounds in _copy_from_iter+0x744/0x10e0 Call Trace: _copy_from_iter+0x744/0x10e0 tcp_sendmsg_locked+0x2290/0x3f80 ksmbd_tcp_writev+0x10c7/0x1ab0 [ksmbd] Allocate room for the padding when the request is a compound, as smb2_read() and smb2_read_pipe() do for their payloads. response_sz is unchanged, so commands still fill only up to it, and kvzalloc() zeroes the padding. Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3") Cc: stable@vger.kernel.org Signed-off-by: Ian Bridges Signed-off-by: Namjae Jeon [ sashal: Retained direct work->conn->vals->max_trans_size access and GFP_KERNEL instead of the local vals pointer and KSMBD_DEFAULT_GFP. ] Signed-off-by: Sasha Levin --- fs/smb/server/smb2pdu.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c index aaccef2e3f3bb..258fc9aaaaa7a 100644 --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -538,7 +538,7 @@ int smb2_allocate_rsp_buf(struct ksmbd_work *work) struct smb2_hdr *hdr = smb_get_msg(work->request_buf); size_t small_sz = MAX_CIFS_SMALL_BUFFER_SIZE; size_t large_sz = small_sz + work->conn->vals->max_trans_size; - size_t sz = small_sz; + size_t sz = small_sz, pad_sz = 0; int cmd = le16_to_cpu(hdr->Command); if (cmd == SMB2_IOCTL_HE || cmd == SMB2_QUERY_DIRECTORY_HE) @@ -560,10 +560,17 @@ int smb2_allocate_rsp_buf(struct ksmbd_work *work) } /* allocate large response buf for chained commands */ - if (le32_to_cpu(hdr->NextCommand) > 0) + if (le32_to_cpu(hdr->NextCommand) > 0) { sz = large_sz; + /* + * is_chained_smb2_message() pads the last response of a + * compound to 8 bytes, which can take it past response_sz. + * Leave room for the padding. kvzalloc() zeroes it. + */ + pad_sz = ALIGN(sz - sizeof(__be32), 8) - (sz - sizeof(__be32)); + } - work->response_buf = kvzalloc(sz, GFP_KERNEL); + work->response_buf = kvzalloc(sz + pad_sz, GFP_KERNEL); if (!work->response_buf) return -ENOMEM; -- 2.53.0