Re: [PATCH] net: ti: icssg-prueth: Check return value to avoid a kernel oops

[Benedikt Spranger <b.spranger@linutronix.de>]

On Sun, 23 Mar 2025 09:19:35 +0200
Roger Quadros <rogerq@kernel.org> wrote:

> Did you actually get a kernel oops?
Yes. And I would like to attach the kernel output, but I do not have
access to the board ATM.

> If yes, which part of code produces the oops.
I get an NULL pointer dereference in is_multicast_ether_addr().
It happens here:

    u32 a = *(const u32 *)addr;

> Even if it fails we do set a random MAC address and do not return
> error. So above statement is false.
I doubt that. of_get_ethdev_address() do not set a random MAC address
in case of a failure. It simply returns -ENODEV. Since
is_valid_ether_addr() fails with a NULL pointer dereference in
is_multicast_ether_addr() on the other hand, no random MAC address is
set. 

> > Check the return value of of_get_ethdev_address() before validating
> > the MAC address.  
> 
> If of_get_ethdev_address() fails the netdev address will remain zero
> (as it was zero initialized during allocation) so
> is_valid_ether_addr() will fail as well.
Yes. It will fail to. But is_valid_ether_addr() is not called any more.

Due to the if statement is_valid_ether_addr() is only called, if
of_get_ethdev_address() exits with 0 aka success. In case of a failure
the if statement is true and there is no call to is_valid_ether_addr().

Regards
    Bene