* Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > On Tue, Oct 6, 2015 at 10:27 AM, Ingo Molnar <mingo@xxxxxxxxxx> wrote: > > > >> > >> We really should try get rid of _all_ uses of the "__" versions unless they are > >> very locally and obviously checked with access_ok(). We've had way too many > >> cases where people thought they were clever, and weren't really. > > > > That's a good idea. > > > > The logistics worries me a bit: it looks like a major undertaking, considering the > > widespread use of these APIs in 1400+ call sites: > > Well, quite frankly, I think I'd be ok with just a mass conversion of the "__" > functions to non-underscore ones. > > From past experience, I don't think we have anything that really cares. The one > exception is probably the signal stack handling, because it really uses multiple > individual accesses, and so it is much more noticeable. > > And there should be *no* meaningful difference between the underscore version > and the non-underscore one, unless somebody does something really odd and > questionable (ie depends on a kernel pointer - which doesn't even work on all > architectures!). > > So I really think we could do a mass conversion of everything that isn't under > "arch/" (and obviously asm-generic/uaccess.h) in just one single go. > > I obviously wouldn't take that into 4.3, but I really don't think this would > merit splitting up into multiple patches either. > > Then, one by one, we might convert back to __get/put_user() when we've (a) added > the SMAP/PAN infrastructure (b) verified that there's an access_ok() > _right_there_ and (c) actually verified that it's performance-critical. > > I see drivers doing __get/put_user(), and it just makes me go "no". Not only are > drivers likely to get it wrong, I don't believe the extra couple of cycles is > going to matter compared to the cost of the hardware access itself. And if the > access_ok() isn't local and obviously in the *only* place that can possibly lead > to that code, then the code shouldn't use the underscore versions. Great, fully agreed and will implement it this way! Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
