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 DA7C43ECBCF; Fri, 4 Sep 2026 06:13:39 +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=1788502421; cv=none; b=M4K3iNNcyOkDkdmXA0//2iSiladF6WhuQBa0Bqt5KGuWJf3aqKPtq/EunHu1nXVPUwnCOIAfPYBO1rUYeadXCbi1z+WgXtfutl8HzDt5yyQyQSeaZCYNjycSlGG+zIc+mm5Hm/1evOByatOtRRXbHlBuRNvqk+hRi5VD4A7VSnw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788502421; c=relaxed/simple; bh=iWzrmmyeDY8ywfxkdknrk7c3u42mF2cP5r2FspCi4yc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Vhy4NF5HwpyLkVWu66aOdZPa1336cw6BgrHfdLhGL47jAUMAsn29cjuUXHRP+SdiVuBHyiimLmxKHv82ruwwle1une13aWByQq5InWAY4vLoOLx94nxoeje8CKfUdW1gFJNrnfLlYpg73S5r1DchWx06yBx0/70eJOJwtGomnQw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=LOOPIa73; 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="LOOPIa73" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3ED321F00A3D; Fri, 4 Sep 2026 06:13:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788502419; bh=jxvU7RTiGHWjjUVFCLkK3czAREPNN+uG07RanTQlODM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=LOOPIa73AfUCGGu5GmPrg5ryYMlDVdojTUL1Fnc362J5VOnPeCj/zYxGuUWgl1BV1 GV9m2uF6Y8y/6j67YauL5XiDujr2fX8JBklHWIty9ONTBT+RUlbJBZfKFEUfzPlm0F RUI89IEK9fOvFHBHEtECuW+SXgT1qEyv3or1vDLA= 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 6.12 201/403] SUNRPC: xdr_buf_trim: clamp buf->len to avoid underflow Date: Fri, 4 Sep 2026 07:00:04 +0200 Message-ID: <20260904045739.424715262@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904045734.806166532@linuxfoundation.org> References: <20260904045734.806166532@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 6.12-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 @@ -2073,7 +2073,7 @@ 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);