tree 3700f94556618f11f37a64e5298cf554b3d90597
parent 7cd10c1149e51a9d2f0868babaf66b8091b9c0b9
author Matthew Dempsky <mdempsky@google.com> 1627435838 -0700
committer Matthew Dempsky <mdempsky@google.com> 1627442833 +0000

runtime: don't crash on nil pointers in checkptrAlignment

Ironically, checkptrAlignment had a latent case of bad pointer
arithmetic: if ptr is nil, then `add(ptr, size-1)` might produce an
illegal pointer value.

The fix is to simply check for nil at the top of checkptrAlignment,
and short-circuit if so.

This CL also adds a more explicit bounds check in checkptrStraddles,
rather than relying on `add(ptr, size-1)` to wrap around. I don't
think this is necessary today, but it seems prudent to be careful.

Fixes #47430.

Change-Id: I5c50b2f7f41415dbebbd803e1b8e7766ca95e1fd
Reviewed-on: https://go-review.googlesource.com/c/go/+/338029
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>