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From:   Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Date:   Sun, 15 Dec 2019 21:34:55 +0100
Message-ID: <CAFBinCAsoE3zFEKbS1Tag=Y_honnpfin625u=N+7QMv4cPy2Wg@mail.gmail.com>
Subject: Re: [PATCH v2] clk: meson: pll: Fix by 0 division in __pll_params_to_rate()
To:     Remi Pommarel <repk@triplefau.lt>
Cc:     Neil Armstrong <narmstrong@baylibre.com>,
        Jerome Brunet <jbrunet@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        Kevin Hilman <khilman@baylibre.com>,
        Michael Turquette <mturquette@baylibre.com>,
        linux-kernel@vger.kernel.org, linux-amlogic@lists.infradead.org,
        linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org
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On Sun, Dec 15, 2019 at 12:39 PM Remi Pommarel <repk@triplefau.lt> wrote:
>
> Some meson pll registers can be initialized with 0 as N value, introducing
> the following division by 0 when computing rate :
>
>   UBSAN: Undefined behaviour in drivers/clk/meson/clk-pll.c:75:9
>   division by zero
>   CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.4.0-rc3-608075-g86c9af8630e1-dirty #400
>   Call trace:
>    dump_backtrace+0x0/0x1c0
>    show_stack+0x14/0x20
>    dump_stack+0xc4/0x100
>    ubsan_epilogue+0x14/0x68
>    __ubsan_handle_divrem_overflow+0x98/0xb8
>    __pll_params_to_rate+0xdc/0x140
>    meson_clk_pll_recalc_rate+0x278/0x3a0
>    __clk_register+0x7c8/0xbb0
>    devm_clk_hw_register+0x54/0xc0
>    meson_eeclkc_probe+0xf4/0x1a0
>    platform_drv_probe+0x54/0xd8
>    really_probe+0x16c/0x438
>    driver_probe_device+0xb0/0xf0
>    device_driver_attach+0x94/0xa0
>    __driver_attach+0x70/0x108
>    bus_for_each_dev+0xd8/0x128
>    driver_attach+0x30/0x40
>    bus_add_driver+0x1b0/0x2d8
>    driver_register+0xbc/0x1d0
>    __platform_driver_register+0x78/0x88
>    axg_driver_init+0x18/0x20
>    do_one_initcall+0xc8/0x24c
>    kernel_init_freeable+0x2b0/0x344
>    kernel_init+0x10/0x128
>    ret_from_fork+0x10/0x18
>
> This checks if N is null before doing the division.
>
> Fixes: 7a29a869434e ("clk: meson: Add support for Meson clock controller")
> Signed-off-by: Remi Pommarel <repk@triplefau.lt>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>

thank you for the patch Remi!


Martin