From nobody Wed Apr 1 22:19:11 2026 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 A3F54405AA6 for ; Wed, 1 Apr 2026 10:57:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775041026; cv=none; b=ANfsM0U+aDN4IJyBHHrLN8yC+BD51WG9NoK/nfMotXEo7YPcs5cxhqleSFBzfTdTRzGd4hpAaMvkb2nmPgE6++xVJzXWh55niyxGH4u9IOqYEhw0EjpA/KmZV66q47zr962sszTIsE4tTSGdKPP1NDe3iNOcG9gZYLjdz9FCzqY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775041026; c=relaxed/simple; bh=i2+6T5laS6iXW24MjsOpSAQSe/11jAwSQhKVgP6EJWc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Ui7sMXfuSC9UthQ59MVqplq6GXY6pQuqqqrby2Qn1qj/47bvqEJKkQATzwVO2lYSex89mwxiWGnMZMeLvKmfOhsXEqEMyjjiOKXOYj6XdE/zVQo0t3z6MNJANybQhtIXBeU50lGWybbDBf2fz1Q/Fpz+E5AarT/+NztjJLMgzE4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=fm7qZddU; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="fm7qZddU" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1775041023; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5LLb+kvWly++E+vGdyFSJ+eIakQ89ZsZ0xRogJGUpqc=; b=fm7qZddUaN8U4xtvycLkYh6BFr3qXhWp+H3Qo1fPqm3ylwWOxM1gepeSPlTzAd2E3oUMRI 0bcKMnO+lutrKbvzAipinQhNTMAkfFDhvSAfndi9Irg53GqboqfLvLdVpveuaYydapf6H/ rn/bmGSDVfzLyCoqK7sRHG+mv8fssNQ= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-526-VsvuYi-5OBS7jgS8dx7PjA-1; Wed, 01 Apr 2026 06:56:58 -0400 X-MC-Unique: VsvuYi-5OBS7jgS8dx7PjA-1 X-Mimecast-MFC-AGG-ID: VsvuYi-5OBS7jgS8dx7PjA_1775041017 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id E8C611956062; Wed, 1 Apr 2026 10:56:56 +0000 (UTC) Received: from warthog.procyon.org.com (unknown [10.44.35.245]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id E9AAD1954102; Wed, 1 Apr 2026 10:56:52 +0000 (UTC) From: David Howells To: netdev@vger.kernel.org Cc: David Howells , Marc Dionne , Jakub Kicinski , "David S. Miller" , Eric Dumazet , Paolo Abeni , linux-afs@lists.infradead.org, linux-kernel@vger.kernel.org, Oleh Konko , Jeffrey Altman , Simon Horman , stable@kernel.org Subject: [PATCH net v4 05/15] rxrpc: Fix RxGK token loading to check bounds Date: Wed, 1 Apr 2026 11:55:58 +0100 Message-ID: <20260401105614.1696001-6-dhowells@redhat.com> In-Reply-To: <20260401105614.1696001-1-dhowells@redhat.com> References: <20260401105614.1696001-1-dhowells@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Content-Type: text/plain; charset="utf-8" From: Oleh Konko rxrpc_preparse_xdr_yfs_rxgk() reads the raw key length and ticket length from the XDR token as u32 values and passes each through round_up(x, 4) before using the rounded value for validation and allocation. When the raw length is >=3D 0xfffffffd, round_up() wraps to 0, so the bounds check and kzalloc both use 0 while the subsequent memcpy still copies the original ~4 GiB value, producing a heap buffer overflow reachable from an unprivileged add_key() call. Fix this by: (1) Rejecting raw key lengths above AFSTOKEN_GK_KEY_MAX and raw ticket lengths above AFSTOKEN_GK_TOKEN_MAX before rounding, consistent with the caps that the RxKAD path already enforces via AFSTOKEN_RK_TIX_MAX. (2) Sizing the flexible-array allocation from the validated raw key length via struct_size_t() instead of the rounded value. (3) Caching the raw lengths so that the later field assignments and memcpy calls do not re-read from the token, eliminating a class of TOCTOU re-parse. The control path (valid token with lengths within bounds) is unaffected. Fixes: 0ca100ff4df6 ("rxrpc: Add YFS RxGK (GSSAPI) security class") Signed-off-by: Oleh Konko Signed-off-by: David Howells Reviewed-by: Jeffrey Altman cc: Marc Dionne cc: Eric Dumazet cc: "David S. Miller" cc: Jakub Kicinski cc: Paolo Abeni cc: Simon Horman cc: linux-afs@lists.infradead.org cc: netdev@vger.kernel.org cc: stable@kernel.org --- net/rxrpc/key.c | 30 +++++++++++++++++------------- 1 file changed, 17 insertions(+), 13 deletions(-) diff --git a/net/rxrpc/key.c b/net/rxrpc/key.c index 26d4336a4a02..77237a82be3b 100644 --- a/net/rxrpc/key.c +++ b/net/rxrpc/key.c @@ -13,6 +13,7 @@ #include #include #include +#include #include #include #include @@ -171,7 +172,7 @@ static int rxrpc_preparse_xdr_yfs_rxgk(struct key_prepa= rsed_payload *prep, size_t plen; const __be32 *ticket, *key; s64 tmp; - u32 tktlen, keylen; + size_t raw_keylen, raw_tktlen, keylen, tktlen; =20 _enter(",{%x,%x,%x,%x},%x", ntohl(xdr[0]), ntohl(xdr[1]), ntohl(xdr[2]), ntohl(xdr[3]), @@ -181,18 +182,22 @@ static int rxrpc_preparse_xdr_yfs_rxgk(struct key_pre= parsed_payload *prep, goto reject; =20 key =3D xdr + (6 * 2 + 1); - keylen =3D ntohl(key[-1]); - _debug("keylen: %x", keylen); - keylen =3D round_up(keylen, 4); + raw_keylen =3D ntohl(key[-1]); + _debug("keylen: %zx", raw_keylen); + if (raw_keylen > AFSTOKEN_GK_KEY_MAX) + goto reject; + keylen =3D round_up(raw_keylen, 4); if ((6 * 2 + 2) * 4 + keylen > toklen) goto reject; =20 ticket =3D xdr + (6 * 2 + 1 + (keylen / 4) + 1); - tktlen =3D ntohl(ticket[-1]); - _debug("tktlen: %x", tktlen); - tktlen =3D round_up(tktlen, 4); + raw_tktlen =3D ntohl(ticket[-1]); + _debug("tktlen: %zx", raw_tktlen); + if (raw_tktlen > AFSTOKEN_GK_TOKEN_MAX) + goto reject; + tktlen =3D round_up(raw_tktlen, 4); if ((6 * 2 + 2) * 4 + keylen + tktlen !=3D toklen) { - kleave(" =3D -EKEYREJECTED [%x!=3D%x, %x,%x]", + kleave(" =3D -EKEYREJECTED [%zx!=3D%x, %zx,%zx]", (6 * 2 + 2) * 4 + keylen + tktlen, toklen, keylen, tktlen); goto reject; @@ -206,7 +211,7 @@ static int rxrpc_preparse_xdr_yfs_rxgk(struct key_prepa= rsed_payload *prep, if (!token) goto nomem; =20 - token->rxgk =3D kzalloc(sizeof(*token->rxgk) + keylen, GFP_KERNEL); + token->rxgk =3D kzalloc(struct_size_t(struct rxgk_key, _key, raw_keylen),= GFP_KERNEL); if (!token->rxgk) goto nomem_token; =20 @@ -221,9 +226,9 @@ static int rxrpc_preparse_xdr_yfs_rxgk(struct key_prepa= rsed_payload *prep, token->rxgk->enctype =3D tmp =3D xdr_dec64(xdr + 5 * 2); if (tmp < 0 || tmp > UINT_MAX) goto reject_token; - token->rxgk->key.len =3D ntohl(key[-1]); + token->rxgk->key.len =3D raw_keylen; token->rxgk->key.data =3D token->rxgk->_key; - token->rxgk->ticket.len =3D ntohl(ticket[-1]); + token->rxgk->ticket.len =3D raw_tktlen; =20 if (token->rxgk->endtime !=3D 0) { expiry =3D rxrpc_s64_to_time64(token->rxgk->endtime); @@ -236,8 +241,7 @@ static int rxrpc_preparse_xdr_yfs_rxgk(struct key_prepa= rsed_payload *prep, memcpy(token->rxgk->key.data, key, token->rxgk->key.len); =20 /* Pad the ticket so that we can use it directly in XDR */ - token->rxgk->ticket.data =3D kzalloc(round_up(token->rxgk->ticket.len, 4), - GFP_KERNEL); + token->rxgk->ticket.data =3D kzalloc(tktlen, GFP_KERNEL); if (!token->rxgk->ticket.data) goto nomem_yrxgk; memcpy(token->rxgk->ticket.data, ticket, token->rxgk->ticket.len);