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 0A6543EBF02; Tue, 21 Jul 2026 18:07:17 +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=1784657238; cv=none; b=rYOFnb/54BgLZOxPWbYBjieOAidssky0nZXPk2m9Is7L0hboqBN7211ELC6/PHftlbNd5oegWexGOJwpR6kUUUUXZQlEdDhe+idP5jFRbCRT+88ttjIaopPNM4tVw6IkiLv+NIWxg01DDOktE91oa8LOkLw6HI/Ld1D5yosJVZU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784657238; c=relaxed/simple; bh=ejCf9URF1Fh9nwki9j63OSXDRbXi8g4L84592e2f3xM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=Awu01Mb3ur1dZ9BrzYZHb7tz9FcskIGmLzN3jR4L7nvg3vKDF6DLWqxCLUqyNeYAJ5g4Rv64UKNmOT+omRPZE92eVa5+8Lz9WZ8d9TtP0FbhHowDUR1yZ/JBW47w8HA+ov/nX3ukh1oSl4oeu4aByLAZn/GL1oI8jGJQOAMlHS0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=eFf1FtXp; 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="eFf1FtXp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 705881F000E9; Tue, 21 Jul 2026 18:07:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784657236; bh=iF7ctUEm70Mlohx64fcrQJZeZaQjja9v0R+/brp7qTc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=eFf1FtXpZ4Ty7uYrGX7SoZTvi4DEPlfNCLNxquftlh+x8MkpAiarwF1ok3rxM0Wyq pRQit/OrqfecKwyFgPi+xIQuKcNggswVNw80DgW3s9VwKko1JuozJGnzLmnvb8IERV UYzOwphfdqGHNFk7fXk+MTBtY6Cw7gjveEo1I5Ao= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, sashiko-bot , Ian Rogers , Don Zickus , Arnaldo Carvalho de Melo , Sasha Levin Subject: [PATCH 6.18 0688/1611] perf tools: Fix get_max_num() size_t underflow on empty sysfs file Date: Tue, 21 Jul 2026 17:13:24 +0200 Message-ID: <20260721152530.856323007@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152514.750365251@linuxfoundation.org> References: <20260721152514.750365251@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-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Arnaldo Carvalho de Melo [ Upstream commit 0a012113bb3a44482c163f16f4db03ccaa37a339 ] get_max_num() reads a sysfs file (cpu/possible, cpu/present, or node/possible) and scans backward from the end to find the last number. If the file is empty, filename__read_str() returns num == 0. The loop `while (--num)` decrements the size_t from 0 to SIZE_MAX, reading backward across the heap until a comma or hyphen is found or unmapped memory is hit. Add an early return for empty files before the backward scan. Fixes: 7780c25bae59fd04 ("perf tools: Allow ability to map cpus to nodes easily") Reported-by: sashiko-bot Reviewed-by: Ian Rogers Cc: Don Zickus Cc: Ian Rogers Assisted-by: Claude:claude-opus-4.6 Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Sasha Levin --- tools/perf/util/cpumap.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/tools/perf/util/cpumap.c b/tools/perf/util/cpumap.c index d0516797a00881..bbf959b443ab1f 100644 --- a/tools/perf/util/cpumap.c +++ b/tools/perf/util/cpumap.c @@ -420,6 +420,12 @@ static int get_max_num(char *path, int *max) buf[num] = '\0'; + /* empty file — nothing to parse */ + if (num == 0) { + err = -1; + goto out; + } + /* start on the right, to find highest node num */ while (--num) { if ((buf[num] == ',') || (buf[num] == '-')) { -- 2.53.0