From: Ralph Campbell rcampbell@nvidia.com
[ Upstream commit 92c77f7c4d5dfaaf45b2ce19360e69977c264766 ]
valid_phys_addr_range() is used to sanity check the physical address range of an operation, e.g., access to /dev/mem. It uses __pa(high_memory) internally.
If memory is populated at the end of the physical address space, then __pa(high_memory) is outside of the physical address space because:
high_memory = (void *)__va(max_pfn * PAGE_SIZE - 1) + 1;
For the comparison in valid_phys_addr_range() this is not an issue, but if CONFIG_DEBUG_VIRTUAL is enabled, __pa() maps to __phys_addr(), which verifies that the resulting physical address is within the valid physical address space of the CPU. So in the case that memory is populated at the end of the physical address space, this is not true and triggers a VIRTUAL_BUG_ON().
Use __pa(high_memory - 1) to prevent the conversion from going beyond the end of valid physical addresses.
Fixes: be62a3204406 ("x86/mm: Limit mmap() of /dev/mem to valid physical addresses") Signed-off-by: Ralph Campbell rcampbell@nvidia.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: Craig Bergstrom craigb@google.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Boris Ostrovsky boris.ostrovsky@oracle.com Cc: Fengguang Wu fengguang.wu@intel.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Hans Verkuil hans.verkuil@cisco.com Cc: Mauro Carvalho Chehab mchehab@s-opensource.com Cc: Peter Zijlstra peterz@infradead.org Cc: Sander Eikelenboom linux@eikelenboom.it Cc: Sean Young sean@mess.org
Link: https://lkml.kernel.org/r/20190326001817.15413-2-rcampbell@nvidia.com Signed-off-by: Sasha Levin (Microsoft) sashal@kernel.org --- 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 1e95d57760cf..b69f7d428443 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 - 1 <= __pa(high_memory - 1); }
/* Can we access it through mmap? Must be a valid physical address: */