[PATCH 5.4 06/32] arm64: Fix kernel address detection of __is_lm_address()

[Greg Kroah-Hartman]

From: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>

commit 519ea6f1c82fcdc9842908155ae379de47818778 upstream.

Currently, the __is_lm_address() check just masks out the top 12 bits
of the address, but if they are 0, it still yields a true result.
This has as a side effect that virt_addr_valid() returns true even for
invalid virtual addresses (e.g. 0x0).

Fix the detection checking that it's actually a kernel address starting
at PAGE_OFFSET.

Fixes: 68dd8ef32162 ("arm64: memory: Fix virt_addr_valid() using __is_lm_address()")
Cc: <stable@xxxxxxxxxxxxxxx> # 5.4.x
Cc: Will Deacon <will@xxxxxxxxxx>
Suggested-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Acked-by: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
Link: https://lore.kernel.org/r/20210126134056.45747-1-vincenzo.frascino@xxxxxxx
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/arm64/include/asm/memory.h |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -247,11 +247,11 @@ static inline const void *__tag_set(cons
 
 
 /*
- * The linear kernel range starts at the bottom of the virtual address
- * space. Testing the top bit for the start of the region is a
- * sufficient check and avoids having to worry about the tag.
+ * Check whether an arbitrary address is within the linear map, which
+ * lives in the [PAGE_OFFSET, PAGE_END) interval at the bottom of the
+ * kernel's TTBR1 address range.
  */
-#define __is_lm_address(addr)	(!(((u64)addr) & BIT(vabits_actual - 1)))
+#define __is_lm_address(addr)	(((u64)(addr) ^ PAGE_OFFSET) < (PAGE_END - PAGE_OFFSET))
 
 #define __lm_to_phys(addr)	(((addr) & ~PAGE_OFFSET) + PHYS_OFFSET)
 #define __kimg_to_phys(addr)	((addr) - kimage_voffset)