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? -- Pavel Begunkov
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