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 9322441B8F6; Fri, 4 Sep 2026 06:13:45 +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=1788502426; cv=none; b=QoQqyjuz0lpVhWNcw/X/miwMsr5e8DJyWBFVuiw3cF4ZckuG9PItRc2H5UnLKC325tCVLYvopVurGHMKmwUbOrgkXfGJ7sH5nJQnUYv1fxDLT4+NZOigpC76d/fxWeLMNN7KA9PtbK2qhjeXJP/NKnF2/7vy1V35GBcYsqnicXM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788502426; c=relaxed/simple; bh=ddArB4j6ONw4QMEvBv57KxAEHljhNkBEo76H7qrT1gI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=VGqGy6hqI6QJx+Iz6/xMkP9Qid+8W7w7ZpB9kCfYWLDvZBwOKjRqzyB+qKiEQefHXkwfGtVKE6FRrbpOWfj2yXwlCAra1ljUJVJGubSidKLYFPsdCy61Wc8Y49IH7Vh1xDJmWcNWYUeGDia57TVwWeNMeIpN1rFqTKW+lX+ncQE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=wGnah0LZ; 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="wGnah0LZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EEAB81F00A3D; Fri, 4 Sep 2026 06:13:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788502425; bh=w04JBfqQiHsp/VoMn+wsBujFaf7OFF4qzQNsjnPbX2c=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=wGnah0LZA/zCYPas4ujWqPy9IOnXiqkx8MjvcowgGFwTKlILP3hcq6SEth/r6g80b fJKjhaIB5OLb+9CMPZrzrHfJJ/7BgFE4aya+ZdR+V44LdJFrC4U5Tx9z/H4e40E7ME p0iRJTiVQI1NabYCx4IOuNni+XL5uhpQMK+1huOc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Chris Mason , Jeff Layton , Chuck Lever Subject: [PATCH 6.12 203/403] SUNRPC: svcauth_gss: enforce krb5 token minimum length Date: Fri, 4 Sep 2026 07:00:06 +0200 Message-ID: <20260904045739.472223179@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904045734.806166532@linuxfoundation.org> References: <20260904045734.806166532@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 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chris Mason commit a919c5c88769cf8fb3ec071e6078d830bf512489 upstream. svcauth_gss_unwrap_priv() validates only an upper bound on the wire-supplied opaque length before handing the buffer to gss_unwrap(): if (len > xdr_stream_remaining(xdr)) goto unwrap_failed; offset = xdr_stream_pos(xdr); ... maj_stat = gss_unwrap(ctx, offset, offset + len, buf); The wire value `len` flows unchanged as the upper bound into the krb5 unwrap path, so a len in [0, 16] passes this check and is handed to gss_unwrap(). For a krb5 v2 context that lands in gss_krb5_unwrap_v2(), which reads the 16-byte RFC 4121 token header fields at ptr+4 and ptr+6 and then calls rotate_left() before any integrity check. With a sub-header length the header reads run past the token, and _rotate_left()'s `shift %= buf->len` path can divide by zero when buf->len has been driven to zero by the truncated token. A header-only token (len == 16) is equally invalid: with a non-zero RRC field and the opaque blob ending at the XDR buffer boundary, rotate_left() builds a zero-length subbuffer, reaching the same division. Reject the token at the server entry point before it reaches the krb5 unwrap core. A valid sealed RFC 4121 token must contain the 16-byte header plus at least some encrypted payload. Fix by adding a minimum-length check immediately after the existing upper-bound check: if (len <= GSS_KRB5_TOK_HDR_LEN) goto unwrap_failed; Fixes: 7c9fdcfb1b64 ("[PATCH] knfsd: svcrpc: gss: server-side implementation of rpcsec_gss privacy") Cc: stable@vger.kernel.org Assisted-by: kres (claude-opus-4-7) Signed-off-by: Chris Mason Reviewed-by: Jeff Layton Link: https://patch.msgid.link/20260524010213.557424-2-cel@kernel.org Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman --- net/sunrpc/auth_gss/svcauth_gss.c | 2 ++ 1 file changed, 2 insertions(+) --- a/net/sunrpc/auth_gss/svcauth_gss.c +++ b/net/sunrpc/auth_gss/svcauth_gss.c @@ -949,6 +949,8 @@ svcauth_gss_unwrap_priv(struct svc_rqst } if (len > xdr_stream_remaining(xdr)) goto unwrap_failed; + if (len <= GSS_KRB5_TOK_HDR_LEN) + goto unwrap_failed; offset = xdr_stream_pos(xdr); saved_len = buf->len;