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 3B3B2418A5B; Sat, 12 Sep 2026 13:38:37 +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=1789220318; cv=none; b=ua8li9xmHkK4a5JPVw5WgDc44FU1yzOXkQui0IzP7pUGRjNqUQkCSl1DdAR38vUD7iYcq55bDjbQaj0b7fPqYDv+V3ylhaf+RAW1h9WsDakmFfjcZZauAC/IX6qi2Cly1uTMzGMqYwNU10aN5A7OZZOMaBFXFhu0Y+E7ol7ix/A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789220318; c=relaxed/simple; bh=WHFcCYDkUzh/W9fb7lH30JYZRwjrhmxnAVC/WE5V9aQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=UptuePLPdAJBWR6v05NbaYRiL/JfrhWPpYnPNzoNOPmPISFMClqVMr4L5sqQHiSyEpftd13xSfkXEkQwNsg1sx70NBFfsK3PgvULDwgEs3PlAq+cH9DCrCjUhunWaTVtnEhv5jNJFoIEJlgkI156Hazf4/xgpfG/Xq40oJHyZGM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=TMcaGNqT; 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="TMcaGNqT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 58AFA1F000FF; Sat, 12 Sep 2026 13:38:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789220317; bh=GDhlMpQGjzvqsUkk3ngQZpMsm+9QNkJ5JISCH0Lorc0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=TMcaGNqTTpp1dfjo58KA7TR0AlojJ37fGZrWuAMfiK9xr4Kjcys6irKGZaqvW4Y+G bTqn3G5aLkd4KmVW3rXYV6CY/0zjHUXd5snLic/VpllV7omO4F8EvyRvLR86PkN6wy wSQMUXhCilQUiIRWQBrexPYdnrVYGCK4mE9mO1Xs= 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 6.6 0151/1424] SUNRPC: svcauth_gss: enforce krb5 token minimum length Date: Sat, 12 Sep 2026 08:43:03 +0200 Message-ID: <20260912065610.678088680@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065607.279695368@linuxfoundation.org> References: <20260912065607.279695368@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 6.6-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 @@ -959,6 +959,8 @@ 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;