On Tue, Sep 06, 2022 at 01:59:53PM -0700 Yury Norov wrote:

On Tue, Sep 06, 2022 at 04:35:42PM -0400, Phil Auld wrote:

...

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") Reported-by: feng xiangjun fengxj325@gmail.com Signed-off-by: Phil Auld pauld@redhat.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: "Rafael J. Wysocki" rafael@kernel.org Cc: Yury Norov yury.norov@gmail.com Cc: stable@vger.kernel.org Cc: feng xiangjun fengxj325@gmail.com

Applied on bitmap-for-next. Thanks!

Great, thanks!

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---

v2: Remove the +/-1 completely from the test since it will produce the same results, and remove some extra parentheses.

include/linux/cpumask.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index bd047864c7ac..e8ad12b5b9d2 100644 --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -1127,9 +1127,10 @@ cpumap_print_list_to_buf(char *buf, const struct cpumask *mask,

• 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) -- 2.31.1