Messages in this thread | | | Date | Tue, 7 Sep 2004 12:15:29 +0200 | From | Jens Axboe <> | Subject | Re: [PATCH] remember to check return value from __copy_to_user() in cdrom_read_cdda_old() |
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On Tue, Sep 07 2004, Andrew Morton wrote: > Jens Axboe <axboe@suse.de> wrote: > > > > On Tue, Sep 07 2004, Andrew Morton wrote: > > > Jens Axboe <axboe@suse.de> wrote: > > > > > > > > On Tue, Sep 07 2004, Paul Mackerras wrote: > > > > > Jens Axboe writes: > > > > > > > > > > > __copy_to_user is the unchecking version of copy_to_user. > > > > > > > > > > It doesn't range-check the address, but it does return non-zero > > > > > (number of bytes not copied) if it encounters a fault writing to the > > > > > user buffer. > > > > > > > > but it doesn't matter, if it returns non-zero then something happened > > > > between the access_ok() and the actual copy because the user app did > > > > something silly. so I don't care much really, I think the major point is > > > > the kernel will cope. > > > > > > > > you could remove the access_ok() and change it to a copy_to_user() > > > > instead, I don't care either way. it's the old and slow interface which > > > > really never is used unless things have gone wrong anyways. > > > > > > > > > > Sure, but at present if an application tries to read cdrom data to address > > > 0x00000000 (say), the kernel will return "success". It should return an > > > error code. (Actually, it should return a short read if any data was > > > transferred, but whatever). > > > > Because access_ok() isn't reliable? > > access_ok() simply checks that the address is in the 0x00000000 - > 0xbfffffff range. We can still get faults in that range.
Ok, it's pretty useless then.
-- Jens Axboe
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