Messages in this thread | | | Subject | Re: [PATCH v3 1/3] of: Move simple-framebuffer device handling from simplefb to of | From | Hector Martin <> | Date | Mon, 13 Dec 2021 20:47:33 +0900 |
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On 13/12/2021 20.30, Javier Martinez Canillas wrote: > On Mon, Dec 13, 2021 at 11:46 AM Hector Martin <marcan@marcan.st> wrote: >> >> On 13/12/2021 17.44, Javier Martinez Canillas wrote: >>> Hello Hector, >>> >>> On Sun, Dec 12, 2021 at 7:24 AM Hector Martin <marcan@marcan.st> wrote: >>>> >>>> This code is required for both simplefb and simpledrm, so let's move it >>>> into the OF core instead of having it as an ad-hoc initcall in the >>>> drivers. >>>> >>>> Acked-by: Thomas Zimmermann <tzimmermann@suse.de> >>>> Signed-off-by: Hector Martin <marcan@marcan.st> >>>> --- >>>> drivers/of/platform.c | 4 ++++ >>>> drivers/video/fbdev/simplefb.c | 21 +-------------------- >>>> 2 files changed, 5 insertions(+), 20 deletions(-) >>>> >>> >>> This is indeed a much better approach than what I suggested. I just >>> have one comment. >>> >>>> diff --git a/drivers/of/platform.c b/drivers/of/platform.c >>>> index b3faf89744aa..793350028906 100644 >>>> --- a/drivers/of/platform.c >>>> +++ b/drivers/of/platform.c >>>> @@ -540,6 +540,10 @@ static int __init of_platform_default_populate_init(void) >>>> of_node_put(node); >>>> } >>>> >>>> + node = of_get_compatible_child(of_chosen, "simple-framebuffer"); >>> >>> You have to check if the node variable is NULL here. >>> >>>> + of_platform_device_create(node, NULL, NULL); >>> >>> Otherwise this could lead to a NULL pointer dereference if debug >>> output is enabled (the node->full_name is printed). >> >> Where is it printed? I thought I might need a NULL check, but this code > > Sorry, I misread of_amba_device_create() as > of_platform_device_create(), which uses the "%pOF" printk format > specifier [0] to print the node's full name as a debug output [1]. > > [0]: https://elixir.bootlin.com/linux/v5.16-rc5/source/Documentation/core-api/printk-formats.rst#L462 > [1]: https://elixir.bootlin.com/linux/v5.16-rc5/source/drivers/of/platform.c#L233 > >> was suggested verbatim by Rob in v2 without the NULL check and digging >> through I found that the NULL codepath is safe. >> > > You are right that passing NULL is a safe code path for now due the > of_device_is_available(node) check, but that seems fragile to me since > just adding a similar debug output to of_platform_device_create() > could trigger the NULL pointer dereference.
Since Rob is the DT maintainer, I'm going to defer to his opinion on this one :-)
-- Hector Martin (marcan@marcan.st) Public Key: https://mrcn.st/pub
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