linux-kernel - [PATCH 5.19 021/207] drivers/base: Fix unsigned comparison to -1 in CPUMAP_FILE_MAX

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Message-Id: <20220926100807.421848068@linuxfoundation.org>
Date:   Mon, 26 Sep 2022 12:10:10 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, "Rafael J. Wysocki" <rafael@...nel.org>,
        Yury Norov <yury.norov@...il.com>,
        feng xiangjun <fengxj325@...il.com>,
        Phil Auld <pauld@...hat.com>
Subject: [PATCH 5.19 021/207] drivers/base: Fix unsigned comparison to -1 in CPUMAP_FILE_MAX_BYTES

From: Phil Auld <pauld@...hat.com>

commit d7f06bdd6ee87fbefa05af5f57361d85e7715b11 upstream.

As PAGE_SIZE is unsigned long, -1 > PAGE_SIZE when NR_CPUS <= 3.
This leads to very large file sizes:

topology$ ls -l
total 0
-r--r--r-- 1 root root 18446744073709551615 Sep  5 11:59 core_cpus
-r--r--r-- 1 root root                 4096 Sep  5 11:59 core_cpus_list
-r--r--r-- 1 root root                 4096 Sep  5 10:58 core_id
-r--r--r-- 1 root root 18446744073709551615 Sep  5 10:10 core_siblings
-r--r--r-- 1 root root                 4096 Sep  5 11:59 core_siblings_list
-r--r--r-- 1 root root 18446744073709551615 Sep  5 11:59 die_cpus
-r--r--r-- 1 root root                 4096 Sep  5 11:59 die_cpus_list
-r--r--r-- 1 root root                 4096 Sep  5 11:59 die_id
-r--r--r-- 1 root root 18446744073709551615 Sep  5 11:59 package_cpus
-r--r--r-- 1 root root                 4096 Sep  5 11:59 package_cpus_list
-r--r--r-- 1 root root                 4096 Sep  5 10:58 physical_package_id
-r--r--r-- 1 root root 18446744073709551615 Sep  5 10:10 thread_siblings
-r--r--r-- 1 root root                 4096 Sep  5 11:59 thread_siblings_list

Adjust the inequality to catch the case when NR_CPUS is configured
to a small value.

Fixes: 7ee951acd31a ("drivers/base: fix userspace break from using bin_attributes for cpumap and cpulist")
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Yury Norov <yury.norov@...il.com>
Cc: stable@...r.kernel.org
Cc: feng xiangjun <fengxj325@...il.com>
Reported-by: feng xiangjun <fengxj325@...il.com>
Signed-off-by: Phil Auld <pauld@...hat.com>
Signed-off-by: Yury Norov <yury.norov@...il.com>
Link: https://lore.kernel.org/r/20220906203542.1796629-1-pauld@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 include/linux/cpumask.h |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -1083,9 +1083,10 @@ cpumap_print_list_to_buf(char *buf, cons
  * cover a worst-case of every other cpu being on one of two nodes for a
  * very large NR_CPUS.
  *
- *  Use PAGE_SIZE as a minimum for smaller configurations.
+ *  Use PAGE_SIZE as a minimum for smaller configurations while avoiding
+ *  unsigned comparison to -1.
  */
-#define CPUMAP_FILE_MAX_BYTES  ((((NR_CPUS * 9)/32 - 1) > PAGE_SIZE) \
+#define CPUMAP_FILE_MAX_BYTES  (((NR_CPUS * 9)/32 > PAGE_SIZE) \
 					? (NR_CPUS * 9)/32 - 1 : PAGE_SIZE)
 #define CPULIST_FILE_MAX_BYTES  (((NR_CPUS * 7)/2 > PAGE_SIZE) ? (NR_CPUS * 7)/2 : PAGE_SIZE)