Commit 90edaac6 authored Oct 27, 2017 by Ingo Molnar

Revert "x86/mm: Limit mmap() of /dev/mem to valid physical addresses"



This reverts commit ce56a86e.

There's unanticipated interaction with some boot parameters like 'mem=',
which now cause the new checks via valid_mmap_phys_addr_range() to be too
restrictive, crashing a Qemu bootup in fact, as reported by Fengguang Wu.

So while the motivation of the change is still entirely valid, we
need a few more rounds of testing to get it right - it's way too late
after -rc6, so revert it for now.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Craig Bergstrom <craigb@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: dsafonov@virtuozzo.com
Cc: kirill.shutemov@linux.intel.com
Cc: mhocko@suse.com
Cc: oleg@redhat.com
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 58c3862b

arch/x86/include/asm/io.h

+0 −4

Original line number	Diff line number	Diff line
		@@ -110,10 +110,6 @@ build_mmio_write(__writeq, "q", unsigned long, "r", )

		#endif

		#define ARCH_HAS_VALID_PHYS_ADDR_RANGE
		extern int valid_phys_addr_range(phys_addr_t addr, size_t size);
		extern int valid_mmap_phys_addr_range(unsigned long pfn, size_t size);

		/**
		* virt_to_phys - map virtual addresses to physical
		* @address: address to remap

arch/x86/mm/mmap.c

+0 −12

Original line number	Diff line number	Diff line
		@@ -174,15 +174,3 @@ const char arch_vma_name(struct vm_area_struct vma)
		return "[mpx]";
		return NULL;
		}

		int valid_phys_addr_range(phys_addr_t addr, size_t count)
		{
		return addr + count <= __pa(high_memory);
		}

		int valid_mmap_phys_addr_range(unsigned long pfn, size_t count)
		{
		phys_addr_t addr = (phys_addr_t)pfn << PAGE_SHIFT;

		return valid_phys_addr_range(addr, count);
		}

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