Commit 4ff53087 authored Jun 15, 2016 by Thomas Garnier Committed by Ingo Molnar Jul 10, 2016

x86/mm: Do not reference phys addr beyond kernel



The new physical address randomized KASLR implementation can cause the
kernel to be aligned close to the end of physical memory. In this case,
_brk_end aligned to PMD will go beyond what is expected safe and hit
the assert in __phys_addr_symbol():

	VIRTUAL_BUG_ON(y >= KERNEL_IMAGE_SIZE);

Instead, perform an inclusive range check to avoid incorrectly triggering
the assert:

	kernel BUG at arch/x86/mm/physaddr.c:38!
	invalid opcode: 0000 [#1] SMP
	...
	RIP: 0010:[<ffffffffbe055721>] __phys_addr_symbol+0x41/0x50
	...
	Call Trace:
	[<ffffffffbe052eb9>] cpa_process_alias+0xa9/0x210
	[<ffffffffbe109011>] ? do_raw_spin_unlock+0xc1/0x100
	[<ffffffffbe051eef>] __change_page_attr_set_clr+0x8cf/0xbd0
	[<ffffffffbe201a4d>] ? vm_unmap_aliases+0x7d/0x210
	[<ffffffffbe05237c>] change_page_attr_set_clr+0x18c/0x4e0
	[<ffffffffbe0534ec>] set_memory_4k+0x2c/0x40
	[<ffffffffbefb08b3>] check_bugs+0x28/0x2a
	[<ffffffffbefa4f52>] start_kernel+0x49d/0x4b9
	[<ffffffffbefa4120>] ? early_idt_handler_array+0x120/0x120
	[<ffffffffbefa4423>] x86_64_start_reservations+0x29/0x2b
	[<ffffffffbefa4568>] x86_64_start_kernel+0x143/0x152

Signed-off-by: Thomas Garnier <thgarnie@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dexuan Cui <decui@microsoft.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sai Praneeth <sai.praneeth.prakhya@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hpe.com>
Link: http://lkml.kernel.org/r/20160615190545.GA26071@www.outflux.net


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 90397a41

arch/x86/mm/pageattr.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -101,7 +101,8 @@ static inline unsigned long highmap_start_pfn(void)

		static inline unsigned long highmap_end_pfn(void)
		{
		return __pa_symbol(roundup(_brk_end, PMD_SIZE)) >> PAGE_SHIFT;
		/* Do not reference physical address outside the kernel. */
		return __pa_symbol(roundup(_brk_end, PMD_SIZE) - 1) >> PAGE_SHIFT;
		}

		#endif
		@@ -112,6 +113,12 @@ within(unsigned long addr, unsigned long start, unsigned long end)
		return addr >= start && addr < end;
		}

		static inline int
		within_inclusive(unsigned long addr, unsigned long start, unsigned long end)
		{
		return addr >= start && addr <= end;
		}

		/*
		* Flushing functions
		*/
		@@ -1316,7 +1323,8 @@ static int cpa_process_alias(struct cpa_data *cpa)
		* to touch the high mapped kernel as well:
		*/
		if (!within(vaddr, (unsigned long)_text, _brk_end) &&
		within(cpa->pfn, highmap_start_pfn(), highmap_end_pfn())) {
		within_inclusive(cpa->pfn, highmap_start_pfn(),
		highmap_end_pfn())) {
		unsigned long temp_cpa_vaddr = (cpa->pfn << PAGE_SHIFT) +
		__START_KERNEL_map - phys_base;
		alias_cpa = *cpa;