> 2019年11月25日 01:52，Pavel Begunkov <asml.silence@xxxxxxxxx> 写道： > > On 24/11/2019 20:10, Jens Axboe wrote: >> On 11/24/19 1:58 AM, Pavel Begunkov wrote: >>> Read/write requests to devices without implemented read/write_iter >>> using fixed buffers causes general protection fault, which totally >>> hangs a machine. >>> >>> io_import_fixed() initialises iov_iter with bvec, but loop_rw_iter() >>> accesses it as iovec, so dereferencing random address. >>> >>> kmap() page by page in this case >> >> This looks good to me, much cleaner/simpler. I've added a few pipe fixed >> buffer tests to liburing as well. Didn't crash for me, but obvious >> garbage coming out. I've flagged this for stable as well. >> > The problem I have is that __user pointer is meant to be checked > for not being a kernel address. I suspect, it could fail in some > device, which double checks the pointer after vfs (e.g. using access_ok()). > Am I wrong? Not a fault at least... > > #define access_ok(...) __range_not_ok(addr, user_addr_max()); > > BTW, is there anybody testing it for non x86-64 arch? > I have some aarch64 platform, What test do you want me to do? -- Jackie Liu
