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 19:45:56 +0900 |
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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 was suggested verbatim by Rob in v2 without the NULL check and digging through I found that the NULL codepath is safe.
of_platform_device_create calls of_platform_device_create_pdata directly, and:
static struct platform_device *of_platform_device_create_pdata( struct device_node *np, const char *bus_id, void *platform_data, struct device *parent) { struct platform_device *dev;
if (!of_device_is_available(np) || of_node_test_and_set_flag(np, OF_POPULATED)) return NULL;
of_device_is_available takes a global spinlock and then calls __of_device_is_available, and that does:
static bool __of_device_is_available(const struct device_node *device) { const char *status; int statlen;
if (!device) return false;
... so I don't see how this can do anything but immediately return false if node is NULL.
-- Hector Martin (marcan@marcan.st) Public Key: https://mrcn.st/pub
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