linux-kernel - Re: [PATCH] mfd: syscon: Don't free allocated name for regmap

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Date:   Tue, 16 Feb 2021 08:34:50 +0200
From:   Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To:     Marc Zyngier <maz@...nel.org>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Cc:     kernel-team@...roid.com, Lee Jones <lee.jones@...aro.org>,
        Arnd Bergmann <arnd@...db.de>, Suman Anna <s-anna@...com>
Subject: Re: [PATCH] mfd: syscon: Don't free allocated name for regmap_config

Hi Marc,

On 03/09/2020 19:02, Marc Zyngier wrote:
> The name allocated for the regmap_config structure is freed
> pretty early, right after the registration of the MMIO region.
> 
> Unfortunately, that doesn't follow the life cycle that debugfs
> expects, as it can access the name field long after the free
> has occured.
> 
> Move the free on the error path, and keep it forever otherwise.
> 
> Fixes: e15d7f2b81d2 ("mfd: syscon: Use a unique name with regmap_config")
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> ---
>  drivers/mfd/syscon.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
> index 75859e492984..7a660411c562 100644
> --- a/drivers/mfd/syscon.c
> +++ b/drivers/mfd/syscon.c
> @@ -108,7 +108,6 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
>  	syscon_config.max_register = resource_size(&res) - reg_io_width;
>  
>  	regmap = regmap_init_mmio(NULL, base, &syscon_config);
> -	kfree(syscon_config.name);
>  	if (IS_ERR(regmap)) {
>  		pr_err("regmap init failed\n");
>  		ret = PTR_ERR(regmap);
> @@ -145,6 +144,7 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
>  	regmap_exit(regmap);
>  err_regmap:
>  	iounmap(base);
> +	kfree(syscon_config.name);
>  err_map:
>  	kfree(syscon);
>  	return ERR_PTR(ret);
> 

This patch causes lots of kmemleak reports, for example:

unreferenced object 0xc8e6f000 (size 64):
  comm "kworker/1:1", pid 22, jiffies 4294938454 (age 95.540s)
  hex dump (first 32 bytes):
    64 73 70 5f 73 79 73 74 65 6d 40 34 30 64 30 30  dsp_system@...00
    30 30 30 00 e0 09 4d c1 ac 1b 4d c1 64 74 4c c1  000...M...M.dtL.
  backtrace:
    [<(ptrval)>] __kmalloc_track_caller+0x2bc/0x418
    [<(ptrval)>] kvasprintf+0x9c/0x124
    [<(ptrval)>] kasprintf+0x70/0xac
    [<(ptrval)>] of_syscon_register+0x1f0/0x4f0
    [<(ptrval)>] device_node_get_regmap+0x12c/0x158
    [<(ptrval)>] syscon_regmap_lookup_by_phandle+0x5c/0x6c
    [<(ptrval)>] omap_iommu_probe+0x6ac/0xc28
    [<(ptrval)>] platform_probe+0x120/0x1e0
    [<(ptrval)>] really_probe+0x2b4/0x121c
    [<(ptrval)>] driver_probe_device+0x10c/0x4c0
    [<(ptrval)>] __device_attach_driver+0x1d8/0x26c
    [<(ptrval)>] bus_for_each_drv+0x174/0x200
    [<(ptrval)>] __device_attach+0x2f0/0x45c
    [<(ptrval)>] device_initial_probe+0x1c/0x20
    [<(ptrval)>] bus_probe_device+0x224/0x2b8
    [<(ptrval)>] device_add+0xad0/0x1e18

 Tomi