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 5999B3F7873; Fri, 4 Sep 2026 05:51:42 +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=1788501103; cv=none; b=ren4d5cbLVztqJu6QFR+3Dsediep9AmLEoN1Vt8zIp3v+tqmXd2Y7EeeZugqczVHFTsTAE8lUbPGduvQ87WvP1C2xmytAWgY7ht2U7mfnnj0pZJ8YF1/p8jCoELmB4rrMc8pHD4BgEXjqvlGjPSm8Ouf21y1hhfKRBJ2iZpFtiU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788501103; c=relaxed/simple; bh=HxYqKWFWSCWe9l8nyC17KB3vFUPaC7uo3eJSzsKPbN4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=sjDgDNuHF768h7luE5Gy8qMbOHO3qQkmUoMK8T4pVRfte4pOo17ca7n5BBi8P+OvpDWvoM4dhVikugUlKI4s8ugtCeBpLDGPoop6vHyRLojAocHf+otmazfzyUU9yahR+g3QColaEUK7u/3Y3iqemOC25/mxVN+FxhT3KQZEXgE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=h6nmdfnD; 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="h6nmdfnD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7B84B1F00A3D; Fri, 4 Sep 2026 05:51:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788501102; bh=uApguYY6rGP8xoepbDqQyUm42GjfNWPTF/pUCI1OXs4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=h6nmdfnD7W465puRH2G6u1ptsYtN0iqwf+C0fH9IHW0eu+/oE15qcnl2aEUXJNlKE cT+UsvxAReSgizDYydhouarazQ0rYEv+3yAyrti52mubBfJeqNJUBcYj2KXEEjIxWC EYHsPI61Jh2xzBGoIBRiar17JGuVz4MpaV1/AZXs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jeff Layton , Chuck Lever Subject: [PATCH 6.18 290/552] SUNRPC: Reject krb5 v2 wrap tokens with oversized ec field Date: Fri, 4 Sep 2026 06:57:27 +0200 Message-ID: <20260904045756.529787171@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904045747.813364717@linuxfoundation.org> References: <20260904045747.813364717@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 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chuck Lever commit ad484748eec0a66eac0f13ab53b3fbedb7333c91 upstream. gss_krb5_unwrap_v2() sets buf->len to a logical length, which can be much smaller than head[0].iov_len (the allocated receive-page capacity). It then calls xdr_buf_trim() with a trim length derived from the 16-bit "extra count" (ec) field in the Kerberos v2 token header. The ec field is authenticated by the post-decrypt memcmp() against the encrypted header copy, so a randomly-mutated value is rejected. However, any peer holding a valid GSS context can legitimately encrypt a token whose ec exceeds the plaintext length. Per RFC 4121, such a token is structurally malformed. Although xdr_buf_trim() now clamps the buf->len subtraction to avoid unsigned underflow, the buffer is still left in a semantically invalid state (zero length, inconsistent iov lengths) when ec is oversized. Reject these tokens before calling xdr_buf_trim(), giving callers a well-defined GSS_S_DEFECTIVE_TOKEN error and keeping the xdr_buf internally consistent. The wrapped blob begins at a nonzero offset -- both callers pass len as offset + opaque_len -- so buf->len still counts the offset bytes that precede the blob. Compare the trim length against the remaining wrapped segment, buf->len - offset, rather than the whole buffer; comparing against buf->len alone leaves an offset-wide window in which an oversized ec passes the test and xdr_buf_trim() cuts into the bytes ahead of the blob. Fixes: cf4c024b9083 ("sunrpc: trim off EC bytes in GSSAPI v2 unwrap") Cc: stable@vger.kernel.org Reviewed-by: Jeff Layton Link: https://patch.msgid.link/20260528-tier2-v1-1-d026a1415e0b@oracle.com Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman --- net/sunrpc/auth_gss/gss_krb5_wrap.c | 2 ++ 1 file changed, 2 insertions(+) --- a/net/sunrpc/auth_gss/gss_krb5_wrap.c +++ b/net/sunrpc/auth_gss/gss_krb5_wrap.c @@ -236,6 +236,8 @@ gss_krb5_unwrap_v2(struct krb5_ctx *kctx buf->len = len - (GSS_KRB5_TOK_HDR_LEN + headskip); /* Trim off the trailing "extra count" and checksum blob */ + if (ec + GSS_KRB5_TOK_HDR_LEN + tailskip > buf->len - offset) + return GSS_S_DEFECTIVE_TOKEN; xdr_buf_trim(buf, ec + GSS_KRB5_TOK_HDR_LEN + tailskip); *align = XDR_QUADLEN(GSS_KRB5_TOK_HDR_LEN + headskip);