Re: [PATCH] nvdimm: Replace the usage of a variable by a direct function call in nd_pfn_validate()

[Markus Elfring <Markus.Elfring@web.de>]

>> The address of a data structure member was determined before
>> a corresponding null pointer check in the implementation of
>> the function “nd_pfn_validate”.
>>
>> Thus avoid the risk for undefined behaviour by replacing the usage of
>> the local variable “parent_uuid” by a direct function call within
>> a later condition check.
>
> Hi Markus,
>
> I think I understand what you are saying above, but I don't follow
> how that applies here. This change seems to be a nice simplification,
> parent_uuid, is used once, just grab it when needed.

Thanks for your positive feedback.


> What is the risk of undefined behavior?

See also:
https://wiki.sei.cmu.edu/confluence/display/c/EXP34-C.+Do+not+dereference+null+pointers?focusedCommentId=405504137#comment-405504137


>> This issue was detected by using the Coccinelle software.
> Which cocci script?

See also:
Reconsidering pointer dereferences before null pointer checks (with SmPL)
https://lore.kernel.org/cocci/1a11455f-ab57-dce0-1677-6beb8492a257@web.de/
https://sympa.inria.fr/sympa/arc/cocci/2023-04/msg00021.html


How do you think about to review and improve any similarly affected software components?

Regards,
Markus