On Tue, Sep 12, 2017 at 04:02:14PM +1000, Dave Chinner wrote: > > Note that one of the bugs there applies to normal read() as well - if you > > are reading from a hole in file into an array with a read-only page in > > the middle, you want a short read. > > And there's another WTF? moment..... > > How do we get a read only page in the middle of an array of pages > we've been told to write data into? And why isn't that a bug in the > code that supplied us with those pages? Sorry, I'd been unclear - I'm talking about read(2) or readv(2) called by userland with a read-only piece in the middle of a (user-supplied) buffer. Either due to mprotect() or simply with one of the iovecs passed to readv(2) having ->iov_base set to some read-only area. It may be a bug in userland code, but when handling that error is as trivial as "don't assume iov_iter_zero(to, n) will return n, use the actual return value", resorting to "the userland code was probably buggy and it's O_DIRECT, so we can do whatever we want" looks wrong. -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
