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 89F74368D47; Sat, 12 Sep 2026 17:09:04 +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=1789232945; cv=none; b=dGizQYNdhrMr7NpEn/3nBA3yqAsYK7ymkj+cnCkmW5hkMQjPbGijtEKBmQ/lM3YKB3ZvwMnAuzv4Q9T9w/5XIvbPiXeppGG4r9VoaEPO/XOfV8GUYIYxcbCN+AT//kKypn1G9vGmE45x3kPpjBBMRxkJWVFY/oJIUdVYTwJmdX8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789232945; c=relaxed/simple; bh=t7yXImrWKqfYqEazI3oB+Sm/1Bweww7evMO3bR4A778=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=dAGcbsjgtzTt2p5jKyFxgZx4fRxO59ofSzgqg2F+lU9U/DWTRusYnQk2ToZJd2FTghZdqrUPUwHzV8euFcAfGBNmLYoRfXT2A6fi4yaFIICxEZ+HMpVi6pVn35kZoKWpaNJq77jjPRF1ou47qaRBei78bX7uotNBXWv287waIYk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=AkcxJTQP; 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="AkcxJTQP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8EAAD1F000FF; Sat, 12 Sep 2026 17:09:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789232944; bh=Z28HvjRJeB0xw8nPL3crY2oLruyteNZJD31GZVjmgVQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=AkcxJTQPfDBQC8XlXLrM7RLrb8pYrWdzGC3/5vkQcmFfDCrtN3/BpM3aksm8M/Omc SFT/uRHut4S97lTBMjf3DRP+5A5blhjcZAIHP96LLMWx13b2YjySiRj1fPjkjEZKei XdkWfhZinedL6Igh/zJN4optIYpU1IlwlZfUp36k= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jeff Layton , Chuck Lever Subject: [PATCH 5.15 113/935] SUNRPC: Reject krb5 v2 wrap tokens with oversized ec field Date: Sat, 12 Sep 2026 08:52:23 +0200 Message-ID: <20260912065529.409611704@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065526.833703348@linuxfoundation.org> References: <20260912065526.833703348@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 5.15-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 @@ -557,6 +557,8 @@ gss_unwrap_kerberos_v2(struct krb5_ctx * 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);