On 2018年01月09日 19:52, Ladislav Michl wrote:
On Tue, Jan 09, 2018 at 05:24:21PM +0800, Qi Hou wrote:
> When more than one GP timers are used as kernel system timers and the
> corresponding nodes in device-tree are marked with the same "disabled"
> property, then the "attr" field of the property will be initialized
> more than once as the property being added to sys file system via
> __of_add_property_sysfs().
>
> In __of_add_property_sysfs(), the "name" field of pp->attr.attr is set
> directly to the return value of safe_name(), without taking care of
> whether it's already a valid pointer to a memory block. If it is, its
> old value will always be overwritten by the new one and the memory block
> allocated before will a "ghost", then a kmemleak happened.
As timers does not seem to be deallocated, this does not matter in practice.
Fix eats a bit more from heap.
Yes, there is no timers being deallocated, as I see.
But it is not eligible that sharing the same property among different
device nodes.
And itexposes kernel info to users. That is not safe.
The fix causes a tiny consumption of heap, maybe it's worth.
--
best regards,
Qi Hou
> That the same "disabled" property being added to different nodes of device
> tree would cause that kind of kmemleak overhead, at leat once.
>
> To fix it, allocate the property dynamically, and delete static one.
>
> Signed-off-by: Qi Hou <qi.hou@xxxxxxxxxxxxx>
> ---
> arch/arm/mach-omap2/timer.c | 19 +++++++++++--------
> 1 file changed, 11 insertions(+), 8 deletions(-)
>
> diff --git a/arch/arm/mach-omap2/timer.c b/arch/arm/mach-omap2/timer.c
> index ece09c9..206ae8d 100644
> --- a/arch/arm/mach-omap2/timer.c
> +++ b/arch/arm/mach-omap2/timer.c
> @@ -156,12 +156,6 @@ static struct clock_event_device clockevent_gpt = {
> .tick_resume = omap2_gp_timer_shutdown,
> };
>
> -static struct property device_disabled = {
> - .name = "status",
> - .length = sizeof("disabled"),
> - .value = "disabled",
> -};
> -
> static const struct of_device_id omap_timer_match[] __initconst = {
> { .compatible = "ti,omap2420-timer", },
> { .compatible = "ti,omap3430-timer", },
> @@ -203,8 +197,17 @@ static struct device_node * __init omap_get_timer_dt(const struct of_device_id *
> of_get_property(np, "ti,timer-secure", NULL)))
> continue;
>
> - if (!of_device_is_compatible(np, "ti,omap-counter32k"))
> - of_add_property(np, &device_disabled);
> + if (!of_device_is_compatible(np, "ti,omap-counter32k")) {
> + struct property *prop;
> +
> + prop = kzalloc(sizeof(*prop), GFP_KERNEL);
> + if (!prop)
> + return NULL;
> + prop->name = "status";
> + prop->length = sizeof("disabled");
> + prop->value = "disabled";
How about (see drivers/of/unittest.c)?
prop->value = "disabled";
prop->length = strlen(prop->value);
It's better. I will do that.
thanks,
Qi Hou
> + of_add_property(np, prop);
> + }
> return np;
> }
>
> --
> 2.7.4
>
> --
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--
Best regards,
Qi Hou
Phone number: +86-10-8477-8608
Address: Floor 15, Building B, Wangjing Plaza, No.9 Zhong-Huan Nanlu, Chaoyang District
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