From: Ralph Campbell <[email protected]>
If CONFIG_DEBUG_VIRTUAL is enabled, a read or write to /dev/mem can
trigger a VIRTUAL_BUG_ON() depending on the value of high_memory.
For example:
read_mem()
valid_phys_addr_range(p=401f1550, count=8)
__pa(high_memory)
__phys_addr(x=ffffc88000000000)
// __START_KERNEL_map = ffffffff80000000
// y = ffffc88000000000 - ffffffff80000000
VIRTUAL_BUG_ON(phys_addr_valid(400000000000))
// boot_cpu_data.x86_phys_bits=46
Since by design high_memory is outside the range of valid physical
addresses, use the non-error checking version __pa_nodebug(high_memory).
Fixes: be62a32044061cb4a3b70a10598e093f1319102e ("x86/mm: Limit mmap() of
/dev/mem to valid physical addresses")
Signed-off-by: Ralph Campbell <[email protected]>
Cc: Craig Bergstrom <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Boris Ostrovsky <[email protected]>
Cc: Fengguang Wu <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Hans Verkuil <[email protected]>
Cc: Mauro Carvalho Chehab <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Sander Eikelenboom <[email protected]>
Cc: Sean Young <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
---
arch/x86/mm/mmap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
index db3165714521..196bed43d5e6 100644
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -230,7 +230,7 @@ bool mmap_address_hint_valid(unsigned long addr, unsigned
long len)
/* Can we access it for direct reading/writing? Must be RAM: */
int valid_phys_addr_range(phys_addr_t addr, size_t count)
{
- return addr + count <= __pa(high_memory);
+ return addr + count <= __pa_nodebug(high_memory);
}
/* Can we access it through mmap? Must be a valid physical address: */
--
2.20.1
