linux-kernel - Re: [PATCH] kernel: initialize cpumask before parsing

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Date:   Thu, 1 Apr 2021 09:34:43 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kernel: initialize cpumask before parsing

On Thu,  1 Apr 2021 14:58:23 +0900
Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp> wrote:

> KMSAN complains that new_value at cpumask_parse_user() from
> write_irq_affinity() from irq_affinity_proc_write() is uninitialized.
> 
>   [  148.133411][ T5509] =====================================================
>   [  148.135383][ T5509] BUG: KMSAN: uninit-value in find_next_bit+0x325/0x340
>   [  148.137819][ T5509]
>   [  148.138448][ T5509] Local variable ----new_value.i@..._affinity_proc_write created at:
>   [  148.140768][ T5509]  irq_affinity_proc_write+0xc3/0x3d0
>   [  148.142298][ T5509]  irq_affinity_proc_write+0xc3/0x3d0
>   [  148.143823][ T5509] =====================================================
> 
> Since bitmap_parse() from cpumask_parse_user() calls find_next_bit(),
> any alloc_cpumask_var() + cpumask_parse_user() sequence has possibility
> that find_next_bit() accesses uninitialized cpu mask variable. Fix this
> problem by replacing alloc_cpumask_var() with zalloc_cpumask_var().
> 
> Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> ---
>  kernel/irq/proc.c    | 4 ++--
>  kernel/profile.c     | 2 +-


>  kernel/trace/trace.c | 2 +-

Acked-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

-- Steve