On Tue, Mar 03, 2020 at 02:34:42PM +0100, Miklos Szeredi wrote: > On Tue, Mar 3, 2020 at 2:14 PM Greg Kroah-Hartman > <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > Unlimited beers for a 21-line kernel patch? Sign me up! > > > > > > Totally untested, barely compiled patch below. > > > > Ok, that didn't even build, let me try this for real now... > > Some comments on the interface: Ok, hey, let's do this proper :) > O_LARGEFILE can be unconditional, since offsets are not exposed to the caller. Good point. > Use the openat2 style arguments; limit the accepted flags to sane ones > (e.g. don't let this syscall create a file). Yeah, I just added that check to my local version: /* Mask off all O_ flags as we only want to read from the file */ flags &= ~(VALID_OPEN_FLAGS); flags |= O_RDONLY | O_LARGEFILE; > If buffer is too small to fit the whole file, return error. Why? What's wrong with just returning the bytes asked for? If someone only wants 5 bytes from the front of a file, it should be fine to give that to them, right? > Verify that the number of bytes read matches the file size, otherwise > return error (may need to loop?). No, we can't "match file size" as sysfs files do not really have a sane "size". So I don't want to loop at all here, one-shot, that's all you get :) Let me actually do this and try it out for real. /me has no idea what he is getting himself into... thanks, greg k-h
