On Sat, 2020-10-03 at 15:55 +0200, Greg Kroah-Hartman wrote: > On Fri, Oct 02, 2020 at 03:30:30PM -0700, Kees Cook wrote: > > On Wed, Sep 30, 2020 at 09:22:19PM -0700, Joe Perches wrote: > > > On Wed, 2020-09-30 at 21:17 -0700, Kees Cook wrote: > > > > On Wed, Sep 30, 2020 at 01:57:40PM +0200, Greg Kroah-Hartman wrote: > > > > > Kees, and Rafael, I don't know if you saw this proposal from Joe for > > > > > sysfs files, questions below: > > > > > > > > I'm a fan. I think the use of sprintf() in sysfs might have been one of > > > > my earliest complaints about unsafe code patterns in the kernel. ;) > > > [] > > > > > > + if (WARN(!buf || offset_in_page(buf), > > > > > > + "invalid sysfs_emit: buf:%p\n", buf)) > > > > > > The dump_stack() is also going to emit pointers > > > so I don't see how it does anything but help > > > show where the buffer was. It is hashed... > > > > dump_stack() is going to report symbols and register contents. > > > > I was just pointing out that %p has no value here[1]. The interesting > > states are: "was it NULL?" "how offset was it?". Its actual content > > won't matter. > > Ok, suggestions for a better error message are always welcome :) For sysfs_emit, the offset_in_buf test also effectively checks if buf not PAGE_SIZE so it helps identify if it is being called from a non _show function. That's actually why %p can be somewhat valuable.
