[PATCH v2] kasan:print the original fault addr when access invalid shadow

[Andrew Morton]

On Mon, 9 Oct 2023 15:37:48 +0800 Haibo Li <haibo.li at mediatek.com> wrote:

> when the checked address is illegal,the corresponding shadow address
> from kasan_mem_to_shadow may have no mapping in mmu table.
> Access such shadow address causes kernel oops.
> Here is a sample about oops on arm64(VA 39bit) 
> with KASAN_SW_TAGS and KASAN_OUTLINE on:
> 
> [ffffffb80aaaaaaa] pgd=000000005d3ce003, p4d=000000005d3ce003,
>     pud=000000005d3ce003, pmd=0000000000000000
> Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
> Modules linked in:
> CPU: 3 PID: 100 Comm: sh Not tainted 6.6.0-rc1-dirty #43
> Hardware name: linux,dummy-virt (DT)
> pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : __hwasan_load8_noabort+0x5c/0x90
> lr : do_ib_ob+0xf4/0x110
> ffffffb80aaaaaaa is the shadow address for efffff80aaaaaaaa.
> The problem is reading invalid shadow in kasan_check_range.
> 
> The generic kasan also has similar oops.
> 
> It only reports the shadow address which causes oops but not
> the original address.
> 
> Commit 2f004eea0fc8("x86/kasan: Print original address on #GP")
> introduce to kasan_non_canonical_hook but limit it to KASAN_INLINE.
> 
> This patch extends it to KASAN_OUTLINE mode.

Is 2f004eea0fc8 a suitable Fixes: target for this?  If not, what is?

Also, I'm assuming that we want to backport this fix into earlier
kernel versions?