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 94CD8415F22; Fri, 4 Sep 2026 05:21:41 +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=1788499302; cv=none; b=cbkF0WbvRCSUiGBJqTgegou3yhQA+R5k14PgGIiErBpsI17zgj30YZql8z0C8sNaL7ebr/qfeT55yTR2p9jvq2dxDdyBLr2OQXwKqfbNgvB9Bn01OubDZn4ptchARi43OQk3XGSuOl6jUpXj2/fwkU8cKz2XxmMYh9dfDc01LuE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788499302; c=relaxed/simple; bh=dHx03CZOHfOvLgZYFqu3zEANPttnugcsya+A/p74lzA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=DPxAmsnByo8QBdTPLnH59bkvbdXqzOhzcsOzA+Vy4JCd3GQ0iKiV+rrjCEaYhrNZmpVY1ojhHZ4ayuzy6fKJn+T1TOUf6RFis9PjMsdPYOSNGKX1PWcqCEjEtnSGoqn/z0oMv2WJKTsPBxYbPvlnJQcuaTI94OLROc11b6/MClY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=gvCMFota; 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="gvCMFota" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EDCAF1F00AC4; Fri, 4 Sep 2026 05:21:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788499301; bh=cOSH4+x7w5W8KCeUu51TH35g7VpbXetSo0gZEs+rPhY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=gvCMFota912hWaob+Qdxry7vZOB8LRov2Hplsyz5g50NXkT5rXp2sKVoLcabskxWD EzVIeE85iEujGibWwFjvRdYAEiPPtiNldVGH7wdpKd5OSSahu9A4VamYunZ3uRKjuy u/laAvtT0ouGu3k8CMBuoIRbtkbqIYVufr4W8Oo4= 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 7.2 370/713] SUNRPC: xdr_buf_trim: clamp buf->len to avoid underflow Date: Fri, 4 Sep 2026 06:55:38 +0200 Message-ID: <20260904045812.121110192@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904045803.810145556@linuxfoundation.org> References: <20260904045803.810145556@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 7.2-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 @@ -2049,7 +2049,7 @@ 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);