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 C34715867D0 for ; Tue, 8 Sep 2026 18:04:37 +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=1788890679; cv=none; b=Cx8sWVjkoe7VQyCbu5APWfl4u0fpAZDvItUGuHeBoNmyu91uSVBTA1WSuSNUYsZdzjhqji0S+3G9PFqBhY7CiO/5lSIBOMcJSFZmmeRO8KeeSvss+GgGBdr3ZiXv+ONYfrAdgdzV14NnAJfhhYSj0fyCV66yQBc8UlQmb+D8zkk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788890679; c=relaxed/simple; bh=WhK7PDhS1yJ07yuJezX/NRTMEY0rFtCu8AOgrXK4nSo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZMITPIuPUNL2FiDzBzfZi9k9Z6u7mRbD6WGBCOAUNRjRpLQ5oVaK+8wOja2SFesv0e2qaRmJrpLN2mffIafbkfjQl8zMOFTKNc1bmV3nb9KCS3tCVvht3KNxcCT1THWExpZFcSLajAAPfXNNPakh6Ecf0mJMw+3dS2nZcT5etao= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=LXNVeZ6I; 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="LXNVeZ6I" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 13C111F00A3E; Tue, 8 Sep 2026 18:04:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788890676; bh=F4iyfWRp0tcYltfMuInKSZTHoGMABx86rZHNzrZeyWk=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=LXNVeZ6I+yPdDh0ICGo921e4604WBAPC4Fi27BM1RHOv1rJsv1drlyAp8e4TUEQTV +ta4XmOkaA6q4ncZcqaN8jqc9UUzfwLkUY9++pyjaebYmFlFc5/RkQv9KG/d1vQV7P JkaOYCeM/K0WYuhOO0Zmq73Nx7DGhbHg4Uo+0Uf/d2RA58YTkRpCZAViivgP3tgau9 e0fbP989ehKMWPTp63BvCCMrUDtuwgi9mIjSPGWI9AT8iEC6R6o9eOQq15zQJyDINo tOYBgFFtvjc+IZ3sRQfbs7ja39w7J2pGJW5fN2vG6LjhJgHho9E2vmEsWhT46eNDdC 03+1neezcsOsg== From: Sasha Levin To: stable@vger.kernel.org Cc: Chris Mason , Jeff Layton , Chuck Lever , Sasha Levin Subject: [PATCH 5.15.y 4/4] SUNRPC: svcauth_gss: enforce krb5 token minimum length Date: Tue, 8 Sep 2026 14:04:32 -0400 Message-ID: <20260908180432.174786-4-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260908180432.174786-1-sashal@kernel.org> References: <2026090352-bamboo-relic-6231@gregkh> <20260908180432.174786-1-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: Chris Mason [ Upstream commit a919c5c88769cf8fb3ec071e6078d830bf512489 ] 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: Sasha Levin --- net/sunrpc/auth_gss/svcauth_gss.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c index afcfdb2f84b6c..77a61bdd1d5ed 100644 --- a/net/sunrpc/auth_gss/svcauth_gss.c +++ b/net/sunrpc/auth_gss/svcauth_gss.c @@ -1003,6 +1003,8 @@ svcauth_gss_unwrap_priv(struct svc_rqst *rqstp, u32 seq, struct gss_ctx *ctx) } 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; -- 2.53.0