On Tue, Jan 26, 2021 at 01:40:56PM +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).
Fix the detection checking that it's actually a kernel address starting at PAGE_OFFSET.
Fixes: f4693c2716b35 ("arm64: mm: extend linear region for 52-bit VA configurations") Cc: stable@vger.kernel.org # 5.4.x
Not sure what happened with the Fixes tag but that's definitely not what it fixes. The above is a 5.11 commit that preserves the semantics of an older commit. So it should be:
Fixes: 68dd8ef32162 ("arm64: memory: Fix virt_addr_valid() using __is_lm_address()")
The above also had a fix for another commit but no need to add two entries, we just fix the original fix: 14c127c957c1 ("arm64: mm: Flip kernel VA space").
Anyway, no need to repost, I can update the fixes tag myself.
In terms of stable backports, it may be cleaner to backport 7bc1a0f9e176 ("arm64: mm: use single quantity to represent the PA to VA translation") which has a Fixes tag already but never made it to -stable. On top of this, we can backport Ard's latest f4693c2716b35 ("arm64: mm: extend linear region for 52-bit VA configurations"). I just tried these locally and the conflicts were fairly trivial.