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From: "Paul E. McKenney" <paulmck@kernel.org>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Kaitao Cheng <pilgrimtao@gmail.com>,
	linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: Re: [PATCH] kernel/smp: Fix an off by one in csd_lock_wait_toolong()
Date: Thu, 09 Jul 2020 16:59:34 +0000	[thread overview]
Message-ID: <20200709165934.GD9247@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <20200709104818.GC20875@mwanda>

On Thu, Jul 09, 2020 at 01:48:18PM +0300, Dan Carpenter wrote:
> The __per_cpu_offset[] array has "nr_cpu_ids" elements so change the >
> >= to prevent a read one element beyond the end of the array.
> 
> Fixes: 0504bc41a62c ("kernel/smp: Provide CSD lock timeout diagnostics")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Good eyes, thank you!  Folding this into the original with
attribution.

							Thanx, Paul

> ---
>  kernel/smp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/smp.c b/kernel/smp.c
> index 78b602cae6c2..f49966713ac3 100644
> --- a/kernel/smp.c
> +++ b/kernel/smp.c
> @@ -171,7 +171,7 @@ static __always_inline bool csd_lock_wait_toolong(call_single_data_t *csd, u64 t
>  		*bug_id = atomic_inc_return(&csd_bug_count);
>  	cpu = csd_lock_wait_getcpu(csd);
>  	smp_mb(); // No stale cur_csd values!
> -	if (WARN_ONCE(cpu < 0 || cpu > nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
> +	if (WARN_ONCE(cpu < 0 || cpu >= nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
>  		cpu_cur_csd = READ_ONCE(per_cpu(cur_csd, 0));
>  	else
>  		cpu_cur_csd = READ_ONCE(per_cpu(cur_csd, cpu));
> -- 
> 2.27.0
> 

      parent reply	other threads:[~2020-07-09 16:59 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-09 10:48 [PATCH] kernel/smp: Fix an off by one in csd_lock_wait_toolong() Dan Carpenter
2020-07-09 10:59 ` Peter Zijlstra
2020-07-09 11:49   ` Sebastian Andrzej Siewior
2020-07-09 14:36     ` Paul E. McKenney
2020-07-09 14:32   ` Paul E. McKenney
2020-07-09 16:59 ` Paul E. McKenney [this message]

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