On 10/18/2022 12:28 PM, Randy Dunlap wrote: > Hi-- > [..] >>>> That said, I realized that not all >>>> architecture implement meaningful kern_addr_valid(), so this line >>>> if ((unsigned long)ptr < PAGE_SIZE || IS_ERR_VALUE(ptr)) >>>> is still need. I'll send v2. >>> >>> Please, add linux-mm@xxxxxxxxx into CC. >> >> Will do. >> >>> I wonder if kern_addr_valid() >>> is safe to use anywhere, especially during early boot. I wonder if >>> it would make sense to implement it on all architectures. >> >> On x86 architecture, kern_addr_valid() looks safe to me though, on >> several other architectures, it's defined (1). > > You might want to compare this patch, which seems to have some support: > > https://lore.kernel.org/lkml/20221018074014.185687-1-wangkefeng.wang@xxxxxxxxxx/ > Thank you for alerting me, appreciated! The patch comment says "copy_from_kernel_nofault() which could check whether the address is a valid kernel address, so no need kern_addr_valid()", I'm afraid copy_from_kernel_nofault() is more of a heavy hammer, and less appropriate for this patch. I'll take a closer look before responding to the submitter. thanks! -jane
