linux-kernel - Re: Kernel panic when reading /sys/firmware/acpi/tables/data/BERT

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Message-ID: <CA+HUmGi_7b1Ywt4dqhqkDds4La=fuAmGaYLGOZHS1+4qrMLaCQ@mail.gmail.com>
Date:   Tue, 19 Nov 2019 17:57:30 -0800
From:   Francesco Ruggeri <fruggeri@...sta.com>
To:     linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        Francesco Ruggeri <fruggeri@...sta.com>
Subject: Re: Kernel panic when reading /sys/firmware/acpi/tables/data/BERT

On Tue, Nov 19, 2019 at 3:30 PM Francesco Ruggeri <fruggeri@...sta.com> wrote:
>
> If I run
>
> for ((i=0; i<10; i++))
>         do for ((j=0; j<1000000; j++))
>                 do cat /sys/firmware/acpi/tables/data/BERT >/dev/null
>         done &
> done
>
> I see this panic in 5.3.11. I see a similar panic in 4.19.84.
>

The issue seems to be that acpi_os_map_cleanup does not execute under
mutex_lock(&acpi_ioremap_lock), so more than one process may end up
freeing the same map.
I will prepare a patch.

Francesco Ruggeri