Re: [PATCH] clk: kirkwood: Fix a clocking boot regression

[Andrew Lunn <andrew@lunn.ch>]

On Sun, Aug 15, 2021 at 01:55:14AM +0200, Linus Walleij wrote:
> Since a few kernel releases the Pogoplug 4 has crashed like this
> during boot:
> 
> Unable to handle kernel NULL pointer dereference at virtual address 00000002
> (...)
> [<c04116ec>] (strlen) from [<c00ead80>] (kstrdup+0x1c/0x4c)
> [<c00ead80>] (kstrdup) from [<c04591d8>] (__clk_register+0x44/0x37c)
> [<c04591d8>] (__clk_register) from [<c04595ec>] (clk_hw_register+0x20/0x44)
> [<c04595ec>] (clk_hw_register) from [<c045bfa8>] (__clk_hw_register_mux+0x198/0x1e4)
> [<c045bfa8>] (__clk_hw_register_mux) from [<c045c050>] (clk_register_mux_table+0x5c/0x6c)
> [<c045c050>] (clk_register_mux_table) from [<c0acf3e0>] (kirkwood_clk_muxing_setup.constprop.0+0x13c/0x1ac)
> [<c0acf3e0>] (kirkwood_clk_muxing_setup.constprop.0) from [<c0aceae0>] (of_clk_init+0x12c/0x214)
> [<c0aceae0>] (of_clk_init) from [<c0ab576c>] (time_init+0x20/0x2c)
> [<c0ab576c>] (time_init) from [<c0ab3d18>] (start_kernel+0x3dc/0x56c)
> [<c0ab3d18>] (start_kernel) from [<00000000>] (0x0)
> Code: e3130020 1afffffb e12fff1e c08a1078 (e5d03000)
> 
> This is because the "powersave" mux clock 0 was provided in an unterminated
> array, which is required by the loop in the driver:
> 
>         /* Count, allocate, and register clock muxes */
>         for (n = 0; desc[n].name;)
>                 n++;
> 
> Here n will go out of bounds and then call clk_register_mux() on random
> memory contents after the mux clock.
> 
> Fix this by terminating the array with a blank entry.
> 
> Fixes: 105299381d87 ("cpufreq: kirkwood: use the powersave multiplexer")
> Cc: stable@vger.kernel.org
> Cc: Andrew Lunn <andrew@lunn.ch>
> Cc: Chris Packham <chris.packham@alliedtelesis.co.nz>
> Cc: Gregory CLEMENT <gregory.clement@bootlin.com>
> Cc: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Thanks Linus

Reviewed-by: Andrew Lunn <andrew@lunn.ch>

    Andrew