Segher Boessenkool <seg...@kernel.crashing.org> writes: > On Tue, Jun 15, 2021 at 03:41:00PM +0200, Jessica Yu wrote: >> +++ Segher Boessenkool [15/06/21 07:50 -0500]: >> >On Tue, Jun 15, 2021 at 02:17:40PM +0200, Jessica Yu wrote: >> >>+int __weak elf_check_module_arch(Elf_Ehdr *hdr) >> >>+{ >> >>+ return 1; >> >>+} >> > >> >But is this a good idea? It isn't useful to be able to attempt to load >> >a module not compiled for your architecture, and it increases the attack >> >surface tremendously. These checks are one of the few things that can >> >*not* be weak symbols, imo. >> >> Hm, could you please elaborate a bit more? This patchset is adding >> extra Elf header checks specifically for powerpc, and the module >> loader usually provides arch-specific hooks via weak symbols. We are >> just providing an new hook here, which should act as a no-op if it >> isn't used. >> >> So if an architecture wants to provide extra header checks, it can do >> so by overriding the new weak symbol. Otherwise, the weak function acts as >> a noop. We also already have the existing elf_check_arch() check for each >> arch and that is *not* a weak symbol. > > The way I read your patch the default elf_check_module_arch does not > call elf_check_arch? Is that clearly called elsewhere and I'm just > dumb again? Sorry for the distraction in that case :-/
Yeah elf_check_arch() is already called from elf_validity_check(), and that call would remain. cheers