Re: [PATCH riscv64] kobject: fix WARNING in input_register_device

Edward Adam Davis
2024-02-08T11:49:06Z

On Thu, 8 Feb 2024 10:56:00, Greg KH wrote:
> > The input_add_uevent_modalias_var()->input_print_modalias() will add 1684 bytes
> > of data to env, which will result in insufficient memory allocated to the buf
> > members of env.
>
> What is "env"? And can you wrap your lines at 72 columns please?
env is an instance of struct kobj_uevent_env.
>
> > Reported-and-tested-by: syzbot+8e41bb0c055b209ebbf4@syzkaller.appspotmail.com
> > Signed-off-by: Edward Adam Davis <eadavis@qq.com>
> > ---
> > include/linux/kobject.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/include/linux/kobject.h b/include/linux/kobject.h
> > index c30affcc43b4..74b37b6459cd 100644
> > --- a/include/linux/kobject.h
> > +++ b/include/linux/kobject.h
> > @@ -30,7 +30,7 @@
> >
> > #define UEVENT_HELPER_PATH_LEN 256
> > #define UEVENT_NUM_ENVP 64 /* number of env pointers */
> > -#define UEVENT_BUFFER_SIZE 2048 /* buffer for the variables */
> > +#define UEVENT_BUFFER_SIZE 2560 /* buffer for the variables */
>
> That's an odd number, why that? Why not just a page? What happens if
> some other path wants more?
An increase of 512 bytes is sufficient for the current issue. Do not consider
the problem of hypothetical existence.
>
> And what's causing the input stack to have so many variables all of a
> sudden, what changed to cause this? Is this a bugfix for a specific
> commit that needs to be backported to older kernels? Why did this
> buffer size all of a sudden be too small?
The result of my analysis is that several members of struct input_dev are too
large, such as its member keybit.

thanks,
edward.