On Thu, 20 Oct 2022, Christoph Hellwig wrote: > On Tue, Oct 18, 2022 at 02:48:01PM -0400, Mike Snitzer wrote: > > > That really does not sound like a good idea at all. And it does not > > > seem to have any MM or core maintainer signoffs. > > > > Sorry, I should've solicited proper review more loudly. > > > > But if you have a specific concern with how DM is looking to use > > is_vmalloc_or_module_addr() please say what that is. > > If I understand the patch correct it tries to use it to detect if > a string is a string global. Besides being nasty API abuse I can't > see how this would even work if DM is built in. It works for built-in DM. You have "kfree_const" that detects if the string points to to .rodata with "is_kernel_rodata". Unfortunatelly, is_kernel_rodata doesn't detect if the string points to some modules's rodata, so we need an extra check for that. So, the logic is: if (!is_vmalloc_or_module_addr(ptr) && !is_kernel_rodata(ptr)) kfree(ptr); I thought about modifying is_kernel_rodata to detect module's rodata as well, but it wouldn't work because kstrdup_const uses it and there would be crash possibility: ptr = kstrdup_const(modules_rodata); unload_module(); use "ptr"; Mikulas
