Hi!
So this explains "mov32 w0, w0" is problematic, and fixes the bug by replacing it with jmp32. Unfortunately, I can't do that in 4.19; plus I don't really see how the bug is solved -- we avoided adding mov32 sequence that triggers the problem, but the problematic sequence could still be produced by the userspace, no?
Does adjust_scalar_min_max_vals still need fixing?
Do you have any hints how to solve this in 4.19?
I have just sent the fixes for 4.14. I sent fixes for 4.19 last Friday.
The problem here is that the verifier assumes the source register has a given value, but the fixups change that value to something else when it is truncated.
The fixups run after the verifier, so a similar sequence produced by userspace will be correctly verified, so no fixes are necessary on adjust_scalar_min_max for this specific issue. The fixed-up code is not verified again.
Thanks, understood.
The challenge in providing those fixes to 4.14 and 4.19 is the absence of JMP32 in those kernels. So, AX was taken as a temporary, so it would still work on JITs.
Yes, I got that far. I have seen the patches for 4.19 and 4.14, and they should fix my problems. Thanks a lot for them.
Best regards, Pavel