Re: [PATCH for-4.18 v1] xen/common: Don't dereference overlay_node after checking that it is NULL

[Julien Grall <julien@xxxxxxx>]

Hi Javi,

Title: Any reason this is titled for-4.18? Shouldn't this patch also be 
merged in staging?
On 09/01/2024 14:19, Javi Merino wrote:
> In remove_nodes(), overlay_node is dereferenced when printing the
> error message even though it is known to be NULLL.  Fix the error
Typo: s/NULLL/NULL/

This can be fixed on commit if there is nothing else.

> message to avoid dereferencing a NULL pointer.
>
> The semantic patch that spots this code is available in
>
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/scripts/coccinelle/null/deref_null.cocci?id=1f874787ed9a2d78ed59cb21d0d90ac0178eceb0
Good catch and glad to see that coccinelle can work on Xen. I am looking 
forward for more work in that area :).
> Fixes: 7e5c4a8b86f1 ("xen/arm: Implement device tree node removal 
> functionalities")
> Signed-off-by: Javi Merino <javi.merino@xxxxxxxxx>
c> ---
> CC: Vikram Garhwal <vikram.garhwal@xxxxxxx>
>
> Vikram, I didn't know what to put in the error message.  Feel free to
> suggest something more appropriate than "Device not present in the
> tree".
More questions for Vikram, looking at the code, it is not 100% clear in 
which condition overlay_node could be NULL. Is this a programming error? 
if so, maybe this should be an ASSERT_UNREACHABLE() (could be added 
separately) and it would be fine to print nothing.
Cheers,

--
Julien Grall