On Wed, Jun 10, 2020 at 08:26:00AM -0400, Qian Cai wrote: > On Wed, Jun 10, 2020 at 07:54:50AM +0200, Dmitry Vyukov wrote: > > On Wed, Jun 10, 2020 at 7:22 AM Qian Cai <cai@xxxxxx> wrote: > > > > > > kernel_init_free_pages() will use memset() on s390 to clear all pages > > > from kmalloc_order() which will override KASAN redzones because a > > > redzone was setup from the end of the allocation size to the end of the > > > last page. Silence it by not reporting it there. An example of the > > > report is, > > > > Interesting. The reason why we did not hit it on x86_64 is because > > clear_page is implemented in asm (arch/x86/lib/clear_page_64.S) and > > thus is not instrumented. Arm64 probably does the same. However, on > > s390 clear_page is defined to memset. > > clear_[high]page are pretty extensively used in the kernel. > > We can either do this, or make clear_page non instrumented on s390 as > > well to match the existing implicit assumption. The benefit of the > > current approach is that we can find some real use-after-free's and > > maybe out-of-bounds on clear_page. The downside is that we may need > > more of these annotations. Thoughts? > > Since we had already done the same thing in poison_page(), I suppose we > could do the same here. Also, clear_page() has been used in many places > on s390, and it is not clear to me if those are all safe like this. > > There might be more annotations required, so it probably up to s390 > maintainers (CC'ed) if they prefer not instrumenting clear_page() like > other arches. Vasily will look into this and come up with a proper solution for s390.
