On Wed 2018-11-14 11:38:19, Andy Shevchenko wrote: > On Wed, Nov 14, 2018 at 12:05:12AM +0100, Petr Mladek wrote: > > On Tue 2018-11-13 14:23:17, Steven Rostedt wrote: > > > On Tue, 13 Nov 2018 13:58:18 -0500 > > > Qian Cai <c...@gmx.us> wrote: > > > > > > > > Care to print the len and name parameters before this line? > > > > len = 60612; name = > > > > > > How big are pages on arm64? Because we shouldn't get to this path if > > > the string is bigger than PAGE_SIZE. But I know that on PPC64, > > > PAGE_SIZE can be 64K, and 60612 is less than that. Thus, if we get > > > there, the test is against signed int:16 (16 bit signed integer) that > > > can go up to most 32768. If the string size is bigger than that, you > > > would get this error. > > > > > > I would just say to ignore it. > > > > I tend to agree. > > > > > The only thing that can happen if > > > someone does this is to trigger the warning. Unless if it is considered > > > a form of DOS, where userspace just bombards the console by triggering > > > this waring. > > > > We are actually on the safe side because it is WARN_ONCE(). > > > > > But I don't see a problem with the actual design. There's > > > no reason we should be processing string variables bigger than 32768 in > > > vsprintf. > > > > It is not even needed in this case. The string is limited also by > > MODULE_NAME_LEN. > > At least not in this code. > > Are you proposing to replace strlen(name) with strnlen(name, MODULE_NAME_LEN)?
It might be a solution. Well, it looks like a wrong design when we would need to use MODULE_NAME_LEN outside module loader code. Also it does not handle other request_module() users that might be affected. On the other hand, I am not sure how a proper solution would look like. request_module() should not limit printk format before the arguments are substituted. The most clean solution probably would be on the vsprintf-level. I mean to limit the precision by the overall string length limit. But it looks a bit weird as well. I still tend to ignore it. The code is safe from the security point of view. The warning would trigger only when completely misused. Best Regards, Petr
