On Fri, 03 Feb 2023 16:28:18 +0530, Anton Gusev wrote > I am trying to investigate a potential NULL dereference > in drivers/firmware/efi/efi.c in the function efi_mem_reserve_persistent. > > In it, a result of memremap call is dereferenced without null checks. > I'd like to understand if it's an error or if there is some sort of invariant that guarantees > it will never return NULL. Indeed, every pointer which can be NULL must be checked for it. The code should check the returned value in rsv for NULL and break. > For this I need to know when memremap (or the underlying ioremap, I guess) > might return NULL. Just looking into its source code didn't give me much insight. > > Do you know any articles/documentation on how memremap and/or ioremap work? > > What topics should I study to understand more about it? There's an article on LWN: https://lwn.net/Articles/653585/, though if you want to understand the mechanics, it seems like you will have to dive into the code. But your observation is indeed correct. You should send a patch. Fixes tag may have 18df7577adae6. Thanks, Siddh _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
