* Re: [PATCH v2] x86: Fix /proc/cpuinfo cpumask warning
[not found] ` <20221012082422.uavybxdfmv4xkhxi@kamzik>
@ 2022-10-12 12:42 ` Andrew Jones
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From: Andrew Jones @ 2022-10-12 12:42 UTC (permalink / raw)
To: x86, linux-kernel
Cc: Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen,
Yury Norov, Jonas Bonn, Stefan Kristiansson, Stafford Horne,
openrisc, Michael Ellerman, linuxppc-dev, Heiko Carstens,
Vasily Gorbik, Alexander Gordeev, linux-s390
Adding more people and lists to CC in order to point this patch out,
because, based on a quick grep of cpuinfo seq operations, I think at least
openrisc, powerpc, and s390 also need an equivalent patch (and I've
already sent a patch for riscv). While the test is simple (see next
paragraph) I'm not equipped to test on each architecture.
To test, just build a kernel with DEBUG_PER_CPU_MAPS enabled, boot to a
shell, do 'cat /proc/cpuinfo', and look for a kernel warning.
Thanks,
drew
On Wed, Oct 12, 2022 at 10:24:22AM +0200, Andrew Jones wrote:
> On Wed, Oct 12, 2022 at 10:19:05AM +0200, Andrew Jones wrote:
> > Commit 78e5a3399421 ("cpumask: fix checking valid cpu range") has
> > started issuing warnings[*] when cpu indices equal to nr_cpu_ids - 1
> > are passed to cpumask_next* functions. seq_read_iter() and cpuinfo's
> > start and next seq operations implement a pattern like
> >
> > n = cpumask_next(n - 1, mask);
> > show(n);
> > while (1) {
> > ++n;
> > n = cpumask_next(n - 1, mask);
> > if (n >= nr_cpu_ids)
> > break;
> > show(n);
> > }
> >
> > which will issue the warning when reading /proc/cpuinfo. Ensure no
> > warning is generated by validating the cpu index before calling
> > cpumask_next().
> >
> > [*] Warnings will only appear with DEBUG_PER_CPU_MAPS enabled.
> >
> > Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
> > Cc: Yury Norov <yury.norov@gmail.com>
> > ---
>
> Forgot the changelog...
>
> v2:
> - Added all the information I should have in the first place to the
> commit message [Boris]
> - Changed style of fix [Boris]
>
> > arch/x86/kernel/cpu/proc.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c
> > index 099b6f0d96bd..94ac02c8dd6f 100644
> > --- a/arch/x86/kernel/cpu/proc.c
> > +++ b/arch/x86/kernel/cpu/proc.c
> > @@ -153,6 +153,9 @@ static int show_cpuinfo(struct seq_file *m, void *v)
> >
> > static void *c_start(struct seq_file *m, loff_t *pos)
> > {
> > + if (*pos >= nr_cpu_ids)
> > + return NULL;
> > +
> > *pos = cpumask_next(*pos - 1, cpu_online_mask);
> > if ((*pos) < nr_cpu_ids)
> > return &cpu_data(*pos);
> > --
> > 2.37.3
> >
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