Messages in this thread | | | Date | Tue, 6 Sep 2022 13:24:44 -0400 | From | Phil Auld <> | Subject | Re: [PATCH] drivers/base: Fix unsigned comparison to -1 in CPUMAP_FILE_MAX_BYTES |
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On Tue, Sep 06, 2022 at 07:02:37PM +0200 Greg Kroah-Hartman wrote: > On Tue, Sep 06, 2022 at 12:04:30PM -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 > > Yeah, lots of CPUs! :) >
Yep, apparently things like lscpu fail with this size.
> > -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> > > --- > > 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..7b1349612d6d 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 + 1) \ > > ? (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 > > > > Nice catch. What type of systems did you run this on to verify it will > work? >
Feng ran it on his 2 cpu laptop. I ran it on my usual test bed (80 cpus) but configured both with NR_CPUS at 8192 and at 2.
It's not really dependent on the actual system. It's a compile time config option. I failed to set it small when testing the first one.
The fix here is just maths :)
With NR_CPUS == 2:
# ls -l /sys/devices/system/cpu/cpu0/topology/ total 0 -r--r--r--. 1 root root 4096 Sep 6 11:40 cluster_cpus -r--r--r--. 1 root root 4096 Sep 6 11:40 cluster_cpus_list -r--r--r--. 1 root root 4096 Sep 6 11:40 cluster_id -r--r--r--. 1 root root 4096 Sep 6 11:40 core_cpus -r--r--r--. 1 root root 4096 Sep 6 11:40 core_cpus_list -r--r--r--. 1 root root 4096 Sep 6 11:40 core_id -r--r--r--. 1 root root 4096 Sep 6 11:29 core_siblings -r--r--r--. 1 root root 4096 Sep 6 11:40 core_siblings_list ...
Cheers, Phil
> thanks, > > greg k-h >
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