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 208414BB7F0 for ; Thu, 3 Sep 2026 14:35:20 +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=1788446124; cv=none; b=FZFkaWRm40R/0YU560KyQHpccmuKzBrfWT6GcSiv67sluO9gVKLAdEz7VBxdXM+NpVPh7rdZiNSkqFopyttPcOdIrM9SMAGyUw21VAVWp+5PaN+9YZwHTLVayUQ8VBqYNTROUGM9jrbRi8rTh0ReU3rjlV7qebwG6i1tKzPKk7o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788446124; c=relaxed/simple; bh=3Z1QZqgjTTnOHMUw+ucq80v225BzkOPZ30uj4ztEWL0=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=uUjtFPYRBGT/gMiNsr+cAOtm1HGU7k4EJG/JRsspO5+XMcp0qEqmUGecvGncVIkHzMFgXr7gVxSYPS/6YFfEto9dXxXKucxfrdb/xIlrR4fFQLGwaflA3JzjETf/A0M8ya+Ag/va+Z9y+SeoW3Rzb5/ovTkT29I1RiILuglqrmk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=OCpp6jX/; 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="OCpp6jX/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 73A231F000E9; Thu, 3 Sep 2026 14:35:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788446118; bh=ZHjJI7JIrXXFWu4MKioze/AubjGJb3E9suvRniZJj7I=; h=Subject:To:Cc:From:Date; b=OCpp6jX/u6UPLQTBMimWtRz5YBMkSUf7R5pW7zG//1gKKCYMo/y3+yZpdnjOZGiuI kMKcbZDnqmcmGLHMUfkZPoCsAuhBKSJPN7q3jlK31KBavWFQ+MXDHTA6JL+jFrzI+t vD4H6dN2aYd+fo/U363+Q2RNYwBv1x83DGpV0K7Q= Subject: FAILED: patch "[PATCH] SUNRPC: Reject short RFC 4121 MIC tokens in" failed to apply to 5.10-stable tree To: chuck.lever@oracle.com,clm@meta.com,jlayton@kernel.org Cc: From: Date: Thu, 03 Sep 2026 16:16:32 +0200 Message-ID: <2026090332-staring-hunchback-c28b@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y git checkout FETCH_HEAD git cherry-pick -x b94f6719dcd9f7a609bc5f459f85795900e77d25 # git commit -s git send-email --to '' --in-reply-to '2026090332-staring-hunchback-c28b@gregkh' --subject-prefix 'PATCH 5.10.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From b94f6719dcd9f7a609bc5f459f85795900e77d25 Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Sat, 23 May 2026 12:52:37 -0400 Subject: [PATCH] SUNRPC: Reject short RFC 4121 MIC tokens in gss_krb5_verify_mic_v2 gss_krb5_verify_mic_v2() reads the token ID at ptr[0..1], the flags byte at ptr[2], and padding at ptr[3..7], then passes ptr + GSS_KRB5_TOK_HDR_LEN and cksum_len to gss_krb5_mic_build_sg(). None of these accesses check read_token->len first. The minimum safe token size is GSS_KRB5_TOK_HDR_LEN (16) plus ctx->krb5e->cksum_len (12-24, depending on the enctype). All callers accept shorter tokens from the wire: - gss_unwrap_resp_integ() enforces only an upper bound (offset + len <= rcv_buf->len) before allocating mic.data = kmalloc(len) and passing it to gss_verify_mic(). A malicious NFS server can therefore supply a short checksum opaque, producing a small slab allocation that the Kerberos MIC verifier reads past. - gss_validate() enforces only len <= RPC_MAX_AUTH_SIZE (400) before passing the wire-supplied length to gss_validate_seqno_mic(), which constructs a mic xdr_netobj and calls gss_verify_mic(). - svcauth_gss_verify_header() enforces only checksum.len >= XDR_UNIT (4 bytes) before dispatching to gss_verify_mic(). - svcauth_gss_unwrap_integ() checks only that the checksum fits in gsd->gsd_scratch. Add a length guard at the top of gss_krb5_verify_mic_v2(), before any ptr[] access or scatterlist construction. Well-formed MIC tokens from gss_krb5_get_mic_v2() already have exactly GSS_KRB5_TOK_HDR_LEN + cksum_len bytes, so valid traffic is unaffected. Reported-by: Chris Mason Fixes: de9c17eb4a91 ("gss_krb5: add support for new token formats in rfc4121") Cc: stable@vger.kernel.org Reviewed-by: Jeff Layton Link: https://patch.msgid.link/20260523165237.510204-1-cel@kernel.org Signed-off-by: Chuck Lever diff --git a/net/sunrpc/auth_gss/gss_krb5_unseal.c b/net/sunrpc/auth_gss/gss_krb5_unseal.c index b5fb70419faa..4d12d49434c2 100644 --- a/net/sunrpc/auth_gss/gss_krb5_unseal.c +++ b/net/sunrpc/auth_gss/gss_krb5_unseal.c @@ -89,6 +89,9 @@ gss_krb5_verify_mic_v2(struct krb5_ctx *ctx, struct xdr_buf *message_buffer, dprintk("RPC: %s\n", __func__); + if (read_token->len < GSS_KRB5_TOK_HDR_LEN + cksum_len) + return GSS_S_DEFECTIVE_TOKEN; + memcpy(&be16_ptr, (char *) ptr, 2); if (be16_to_cpu(be16_ptr) != KG2_TOK_MIC) return GSS_S_DEFECTIVE_TOKEN;