On Tue, Jan 26, 2021 at 11:58:13AM +0000, Vincenzo Frascino wrote: > On 1/25/21 5:56 PM, Catalin Marinas wrote: > > On Mon, Jan 25, 2021 at 04:09:57PM +0000, Vincenzo Frascino wrote: > >> On 1/25/21 2:59 PM, Catalin Marinas wrote: > >>> On Mon, Jan 25, 2021 at 02:36:34PM +0000, Vincenzo Frascino wrote: > >>>> On 1/25/21 1:02 PM, Mark Rutland wrote: > >>>>> On Fri, Jan 22, 2021 at 03:56:40PM +0000, Vincenzo Frascino wrote: > >>>>>> Currently, the __is_lm_address() check just masks out the top 12 bits > >>>>>> of the address, but if they are 0, it still yields a true result. > >>>>>> This has as a side effect that virt_addr_valid() returns true even for > >>>>>> invalid virtual addresses (e.g. 0x0). > >>>>>> > >>>>>> Improve the detection checking that it's actually a kernel address > >>>>>> starting at PAGE_OFFSET. > >>>>>> > >>>>>> Cc: Catalin Marinas <catalin.mari...@arm.com> > >>>>>> Cc: Will Deacon <w...@kernel.org> > >>>>>> Suggested-by: Catalin Marinas <catalin.mari...@arm.com> > >>>>>> Reviewed-by: Catalin Marinas <catalin.mari...@arm.com> > >>>>>> Signed-off-by: Vincenzo Frascino <vincenzo.frasc...@arm.com> > >>>>> > >>>>> Looking around, it seems that there are some existing uses of > >>>>> virt_addr_valid() that expect it to reject addresses outside of the > >>>>> TTBR1 range. For example, check_mem_type() in drivers/tee/optee/call.c. > >>>>> > >>>>> Given that, I think we need something that's easy to backport to stable. > >>>>> > >>>> > >>>> I agree, I started looking at it this morning and I found cases even in > >>>> the main > >>>> allocators (slub and page_alloc) either then the one you mentioned. > >>>> > >>>>> This patch itself looks fine, but it's not going to backport very far, > >>>>> so I suspect we might need to write a preparatory patch that adds an > >>>>> explicit range check to virt_addr_valid() which can be trivially > >>>>> backported. > >>>>> > >>>> > >>>> I checked the old releases and I agree this is not back-portable as it > >>>> stands. > >>>> I propose therefore to add a preparatory patch with the check below: > >>>> > >>>> #define __is_ttrb1_address(addr) ((u64)(addr) >= PAGE_OFFSET && \ > >>>> (u64)(addr) < PAGE_END) > >>>> > >>>> If it works for you I am happy to take care of it and post a new version > >>>> of my > >>>> patches. > >>> > >>> I'm not entirely sure we need a preparatory patch. IIUC (it needs > >>> checking), virt_addr_valid() was fine until 5.4, broken by commit > >>> 14c127c957c1 ("arm64: mm: Flip kernel VA space"). Will addressed the > >>> flip case in 68dd8ef32162 ("arm64: memory: Fix virt_addr_valid() using > >>> __is_lm_address()") but this broke the <PAGE_OFFSET case. So in 5.4 a > >>> NULL address is considered valid. > >>> > >>> Ard's commit f4693c2716b3 ("arm64: mm: extend linear region for 52-bit > >>> VA configurations") changed the test to no longer rely on va_bits but > >>> did not change the broken semantics. > >>> > >>> If Ard's change plus the fix proposed in this test works on 5.4, I'd say > >>> we just merge this patch with the corresponding Cc stable and Fixes tags > >>> and tweak it slightly when doing the backports as it wouldn't apply > >>> cleanly. IOW, I wouldn't add another check to virt_addr_valid() as we > >>> did not need one prior to 5.4. > >> > >> Thank you for the detailed analysis. I checked on 5.4 and it seems that Ard > >> patch (not a clean backport) plus my proposed fix works correctly and > >> solves the > >> issue. > > > > I didn't mean the backport of the whole commit f4693c2716b3 as it > > probably has other dependencies, just the __is_lm_address() change in > > that patch. > > Then call it preparatory patch ;)
It's preparatory only for the stable backports, not for current mainline. But I'd rather change the upstream patch when backporting to apply cleanly, no need for a preparatory stable patch. -- Catalin