On 10/26/20 6:05 PM, Al Viro wrote: > On Mon, Oct 26, 2020 at 05:56:11PM -0600, Jens Axboe wrote: >> On 10/26/20 4:55 PM, Kyle Huey wrote: >>> A test program from the rr[0] test suite, vm_readv_writev[1], no >>> longer works on 5.10-rc1 when compiled as a 32 bit binary and executed >>> on a 64 bit kernel. The first process_vm_readv call (on line 35) now >>> fails with EFAULT. I have bisected this to >>> c3973b401ef2b0b8005f8074a10e96e3ea093823. >>> >>> It should be fairly straightforward to extract the test case from our >>> repository into a standalone program. >> >> Can you check with this applied? >> >> diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c >> index fd12da80b6f2..05676722d9cd 100644 >> --- a/mm/process_vm_access.c >> +++ b/mm/process_vm_access.c >> @@ -273,7 +273,8 @@ static ssize_t process_vm_rw(pid_t pid, >> return rc; >> if (!iov_iter_count(&iter)) >> goto free_iov_l; >> - iov_r = iovec_from_user(rvec, riovcnt, UIO_FASTIOV, iovstack_r, false); >> + iov_r = iovec_from_user(rvec, riovcnt, UIO_FASTIOV, iovstack_r, >> + in_compat_syscall()); > > _ouch_ > > There's a bug, all right, but I'm not sure that this is all there is > to it. For now it's probably the right fix, but... Consider the fun > trying to use that from 32bit process to access the memory of 64bit > one. IOW, we might want to add an explicit flag for "force 64bit > addresses/sizes in rvec". Ouch yes good point, nice catch. -- Jens Axboe
