[PATCH] arm64: mm: Fix pfn_is_map_memory() misreporting mapped memory

[Vladimir Murzin]

Commit 7ace06a01efa ("arm64: mm: fix accidental linear mapping of
no-map reserved memory") removed sub-page no-map regions from the
linear mapping. However, pfn_is_map_memory() can still report that
such a region is mapped.

For instance, with 64K pages, say we have

normal:        ...–0xa2007fff
no-map: 0xa2008000–0xa200ffff
normal: 0xa2010000–...

The range 0xa2000000–0xa200ffff is not linearly mapped, but
pfn_is_map_memory(__phys_to_pfn(0xa2008000)) aligns the address to
page granularity and passes 0xa2000000 to memblock_is_map_memory().
That address belongs to the preceding normal memblock region, so the
no-map region is ignored and the function returns true.

Fix that by checking if entire page is subset of memory block.

Fixes: 7ace06a01efa ("arm64: mm: fix accidental linear mapping of no-map reserved memory")
Assisted-by: LLM
Signed-off-by: Vladimir Murzin <vladimir.murzin at arm.com>
---
 arch/arm64/mm/init.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index fbf215ecc7d0..5da80e1e1727 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -172,7 +172,8 @@ int pfn_is_map_memory(unsigned long pfn)
 	if (PHYS_PFN(addr) != pfn)
 		return 0;
 
-	return memblock_is_map_memory(addr);
+	return memblock_is_region_memory(addr, PAGE_SIZE) &&
+		memblock_is_map_memory(addr);
 }
 EXPORT_SYMBOL(pfn_is_map_memory);
 
-- 
2.34.1