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 573CD2F260C; Sat, 12 Sep 2026 19:27:29 +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=1789241250; cv=none; b=rpJ9Gm1wvKyL6QxUlUcx2itlN+8WD6xrxzgwnQnuobe0VZADeV6xv9/XupS+uI3Eefh/Cm403+x7mPXL1HbyM2g7Bafu82nCHV4bdt7j4wM0yaz9KSdmq6oeISyIZaPO/Gvkik0scp1wMXbpCUJxFi1yIKgXPqBNxUYSGdYaHsM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789241250; c=relaxed/simple; bh=yokclUy2Tk1AJwvdqWQta1Sv7FrBWiT1RSu3LlEWMUc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ommXTgOyKvHKEgKg2XciPO2kMhyyDROh8FiP5TNvoU2SXrS/NqbtUWocJGpbubQYFvGjDIJV751rHCD+uzQcBShkh0E2rrDperCca8kv5X7JpKl0ndhlW22qy3utqNfiBWaj4WQwPKOYKxrE0lCc19Cy42A1/ToWJ5LqhaE6uy0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=b11Q2rll; 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="b11Q2rll" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 29CF31F000FF; Sat, 12 Sep 2026 19:27:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789241249; bh=F09B8I9iQzdcuMtYtOknix1Sj0dLstDlREW5WQRYk7A=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=b11Q2rllibcwL5u9IaihQVOcRjIFmypwpKY17u6xHK2Mbsfa1j0I6IZxcTGVSasMz TcsncElyBh6MCUgX6bGZyeCw1YyzJmIVQeSl/0gEG8eZ2+MssB0z1GwhHKJvNQiLsp 3JHCPvA7vokju+kPEvhGSwYQvmRZOL9wUQEqRfn0= 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 5.10 095/798] SUNRPC: xdr_buf_trim: clamp buf->len to avoid underflow Date: Sat, 12 Sep 2026 08:55:23 +0200 Message-ID: <20260912065519.133981219@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065516.948645775@linuxfoundation.org> References: <20260912065516.948645775@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 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chris Mason commit 3f491306dcb673ff5e78e1044ba450c58978774e upstream. xdr_buf_trim() trims `len` bytes from the tail of an xdr_buf by walking the tail, pages, and head iovecs. Each per-section step uses min_t() so it never removes more bytes than that section holds, but the final accounting at the fix_len label subtracts the total bytes actually consumed from buf->len without any clamp: fix_len: buf->len -= (len - trim); When the caller has set buf->len to a value smaller than the sum of the iov_lens, (len - trim) can exceed buf->len and the unsigned subtraction wraps to near UINT_MAX. gss_krb5_unwrap_v2() reaches xdr_buf_trim() in exactly that state: buf->head[0].iov_len -= GSS_KRB5_TOK_HDR_LEN + headskip; buf->len = len - (GSS_KRB5_TOK_HDR_LEN + headskip); xdr_buf_trim(buf, ec + GSS_KRB5_TOK_HDR_LEN + tailskip); buf->len is a small wire-derived value while the iov_lens are at page scale, so the per-section loops legitimately consume far more bytes than buf->len records. The wrapped buf->len then propagates as the authoritative stream bound into every downstream XDR decoder. Fix by clamping the decrement so buf->len bottoms out at zero: buf->len -= min_t(unsigned int, buf->len, len - trim); On the normal path where the iov_lens sum to buf->len, (len - trim) is always <= buf->len and the result is identical to before. No callers change behavior outside the underflow case. Fixes: 4c190e2f913f ("sunrpc: trim off trailing checksum before returning decrypted or integrity authenticated buffer") 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/20260524010213.557424-4-cel@kernel.org Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman --- net/sunrpc/xdr.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/sunrpc/xdr.c +++ b/net/sunrpc/xdr.c @@ -1519,7 +1519,7 @@ void xdr_buf_trim(struct xdr_buf *buf, u trim -= cur; } fix_len: - buf->len -= (len - trim); + buf->len -= min_t(unsigned int, buf->len, len - trim); } EXPORT_SYMBOL_GPL(xdr_buf_trim);