On 5/23/23 8:48?PM, Jeff Xu wrote: > Hi > I have a question on the protection key in io_uring. Today, when a > user thread enters the kernel through syscall, PKRU is preserved, and > the kernel will respect the PKEY protection of memory. > > For example: > sys_mprotect_pkey((void *)ptr, size, PROT_READ | PROT_WRITE, pkey); > pkey_write_deny(pkey); <-- disable write access to pkey for this thread. > ret = read(fd, ptr, 1); <-- this will fail in the kernel. > > I wonder what is the case for io_uring, since read is now async, will > kthread have the user thread's PKUR ? There is no kthread. What can happen is that some operation may be punted to the io-wq workers, but these act exactly like a thread created by the original task. IOW, if normal threads retain the protection key, so will any io-wq io_uring thread. If they don't, they do not. > In theory, it is possible, i.e. from io_uring_enter syscall. But I > don't know the implementation details of io_uring, hence asking the > expert in this list. Right, if the IO is done inline, then it won't make a difference if eg read(2) is used or IORING_OP_READ (or similar) with io_uring. -- Jens Axboe
