linux-kernel - Re: [PATCH v2] clk: meson: pll: Fix by 0 division in __pll_params_to

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Message-ID: <1jmubsbjn8.fsf@starbuckisacylon.baylibre.com>
Date:   Mon, 16 Dec 2019 12:21:47 +0100
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Remi Pommarel <repk@...plefau.lt>
Cc:     Neil Armstrong <narmstrong@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Kevin Hilman <khilman@...libre.com>,
        Michael Turquette <mturquette@...libre.com>,
        linux-kernel@...r.kernel.org, linux-amlogic@...ts.infradead.org,
        linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2] clk: meson: pll: Fix by 0 division in __pll_params_to_rate()


On Sun 15 Dec 2019 at 21:34, Martin Blumenstingl <martin.blumenstingl@...glemail.com> wrote:

> On Sun, Dec 15, 2019 at 12:39 PM Remi Pommarel <repk@...plefau.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@...plefau.lt>
> Reviewed-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>

Applied with a slightly more detailed comment.
Thx

>
> thank you for the patch Remi!
>
>
> Martin