Re: [PATCH 2/2] mm: kmsan: handle alloc failures in kmsan_ioremap_page_range()

[Andrew Morton]

On Wed, 12 Apr 2023 16:53:00 +0200 Alexander Potapenko <glider@xxxxxxxxxx> wrote:

> Similarly to kmsan_vmap_pages_range_noflush(),
> kmsan_ioremap_page_range() must also properly handle allocation/mapping
> failures. In the case of such, it must clean up the already created
> metadata mappings and return an error code, so that the failure can be
> propagated to ioremap_page_range().

Unlike [1/2], this changelog doesn't describe the user-visible effects.
A bit of clicking takes me to

: kmsan's allocation of shadow or origin memory in
: kmsan_vmap_pages_range_noflush() fails silently due to fault injection
: (FI).  KMSAN sort of "swallows" the allocation failure, and moves on. 
: When either of them is later accessed while updating the metadata,
: there are no checks to test the validity of the respective pointers,
: which results in a page fault.

So I'll add that to the changelog and shall add cc:stable to both patches.