On Sun, Apr 24, 2022 at 11:19:05PM +0200, Ard Biesheuvel wrote:
On Sun, 24 Apr 2022 at 19:22, Mike Rapoport rppt@kernel.org wrote:
From: Mike Rapoport rppt@linux.ibm.com
The semantics of pfn_valid() is to check presence of the memory map for a PFN and not whether a PFN is covered by the linear map. The memory map may be present for NOMAP memory regions, but they won't be mapped in the linear mapping. Accessing such regions via __va() when they are memremap()'ed will cause a crash.
...
diff --git a/kernel/iomem.c b/kernel/iomem.c index 62c92e43aa0d..e85bed24c0a9 100644 --- a/kernel/iomem.c +++ b/kernel/iomem.c @@ -33,7 +33,7 @@ static void *try_ram_remap(resource_size_t offset, size_t size, unsigned long pfn = PHYS_PFN(offset);
/* In the simple case just return the existing linear address */
if (pfn_valid(pfn) && !PageHighMem(pfn_to_page(pfn)) &&
if (!PageHighMem(pfn_to_page(pfn)) &&This looks wrong to me. Calling any of the PageXxx() accessors is only safe if the PFN is valid, since otherwise, we don't know if the associated struct page exists.
Yeah, you are right, was over-enthusiastic here...
arch_memremap_can_ram_remap(offset, size, flags)) return __va(offset);base-commit: b2d229d4ddb17db541098b83524d901257e93845
2.28.0