On 2024/3/6 4:09, Matthew Wilcox wrote: > On Mon, Mar 04, 2024 at 08:31:56PM +0800, Miaohe Lin wrote: >> On 2024/3/1 5:20, Matthew Wilcox (Oracle) wrote: >>> The only user of this function calls page_address_in_vma() immediately >>> after page_mapped_in_vma() calculates it and uses it to return true/false. >>> Return the address instead, allowing memory-failure to skip the call >>> to page_address_in_vma(). >> >> IIUC, this patch will change the semantic slightly. There is one corner >> case where page_mapped_in_vma() returns true but page_address_in_vma() >> returns -EFAULT if mremap is done after the check. In that case, >> SIGKILL will be sent to the user. But with this patch applied, SIGBUS >> will be sent to the user with address before doing mremap. Or am I >> miss something? > > Isn't that an example of a race that userspace can't possibly rely on? You're right. Userspace shouldn't possibly rely on it. Thanks. > It can't observe where the kernel has got to in its processing of the > fault, so it's OK if we behave if the mremap() has happened before, > during or after the two calls. > . >
