Commit 44b04912 authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Ingo Molnar
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x86/mpx: Do not allow MPX if we have mappings above 47-bit 



MPX (without MAWA extension) cannot handle addresses above 47 bits, so we
need to make sure that MPX cannot be enabled if we already have a VMA above
the boundary and forbid creating such VMAs once MPX is enabled.

The patch implements mpx_unmapped_area_check() which is called from all
variants of get_unmapped_area() to check if the requested address fits
mpx.

On enabling MPX, we check if we already have any vma above 47-bit
boundary and forbit the enabling if we do.

As long as DEFAULT_MAP_WINDOW is equal to TASK_SIZE_MAX, the change is
nop. It will change when we allow userspace to have mappings above
47-bits.

Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20170716225954.74185-6-kirill.shutemov@linux.intel.com


[ Readability edits. ]
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent e8f01a8d

arch/x86/include/asm/mpx.h

+9 −0
Original line number Diff line number Diff line
@@ -73,6 +73,9 @@ static inline void mpx_mm_init(struct mm_struct *mm) 
}

void mpx_notify_unmap(struct mm_struct *mm, struct vm_area_struct *vma,

		      unsigned long start, unsigned long end);



unsigned long mpx_unmapped_area_check(unsigned long addr, unsigned long len,

		unsigned long flags);

#else

static inline siginfo_t *mpx_generate_siginfo(struct pt_regs *regs)

{
@@ -94,6 +97,12 @@ static inline void mpx_notify_unmap(struct mm_struct *mm, 
				    unsigned long start, unsigned long end)

{

}



static inline unsigned long mpx_unmapped_area_check(unsigned long addr,

		unsigned long len, unsigned long flags)

{

	return addr;

}

#endif /* CONFIG_X86_INTEL_MPX */



#endif /* _ASM_X86_MPX_H */

arch/x86/include/asm/processor.h

+3 −0
Original line number Diff line number Diff line
@@ -809,6 +809,7 @@ static inline void spin_lock_prefetch(const void *x) 
#define IA32_PAGE_OFFSET	PAGE_OFFSET

#define TASK_SIZE		PAGE_OFFSET

#define TASK_SIZE_MAX		TASK_SIZE

#define DEFAULT_MAP_WINDOW	TASK_SIZE

#define STACK_TOP		TASK_SIZE

#define STACK_TOP_MAX		STACK_TOP
@@ -850,6 +851,8 @@ static inline void spin_lock_prefetch(const void *x) 
 */

#define TASK_SIZE_MAX	((1UL << 47) - PAGE_SIZE)



#define DEFAULT_MAP_WINDOW	TASK_SIZE_MAX



/* This decides where the kernel will search for a free chunk of vm

 * space during mmap's.

 */

arch/x86/kernel/sys_x86_64.c

+9 −0
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ 
#include <asm/compat.h>

#include <asm/ia32.h>

#include <asm/syscalls.h>

#include <asm/mpx.h>



/*

 * Align a virtual address to avoid aliasing in the I$ on AMD F15h.
@@ -132,6 +133,10 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr, 
	struct vm_unmapped_area_info info;

	unsigned long begin, end;



	addr = mpx_unmapped_area_check(addr, len, flags);

	if (IS_ERR_VALUE(addr))

		return addr;



	if (flags & MAP_FIXED)

		return addr;
@@ -171,6 +176,10 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, 
	unsigned long addr = addr0;

	struct vm_unmapped_area_info info;



	addr = mpx_unmapped_area_check(addr, len, flags);

	if (IS_ERR_VALUE(addr))

		return addr;



	/* requested length too big for entire address space */

	if (len > TASK_SIZE)

		return -ENOMEM;

arch/x86/mm/hugetlbpage.c

+6 −0
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ 
#include <asm/tlbflush.h>

#include <asm/pgalloc.h>

#include <asm/elf.h>

#include <asm/mpx.h>



#if 0	/* This is just for testing */

struct page *
@@ -135,6 +136,11 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr, 


	if (len & ~huge_page_mask(h))

		return -EINVAL;



	addr = mpx_unmapped_area_check(addr, len, flags);

	if (IS_ERR_VALUE(addr))

		return addr;



	if (len > TASK_SIZE)

		return -ENOMEM;

arch/x86/mm/mpx.c

+32 −1
Original line number Diff line number Diff line
@@ -355,10 +355,19 @@ int mpx_enable_management(void) 
	 */

	bd_base = mpx_get_bounds_dir();

	down_write(&mm->mmap_sem);



	/* MPX doesn't support addresses above 47 bits yet. */

	if (find_vma(mm, DEFAULT_MAP_WINDOW)) {

		pr_warn_once("%s (%d): MPX cannot handle addresses "

				"above 47-bits. Disabling.",

				current->comm, current->pid);

		ret = -ENXIO;

		goto out;

	}

	mm->context.bd_addr = bd_base;

	if (mm->context.bd_addr == MPX_INVALID_BOUNDS_DIR)

		ret = -ENXIO;



out:

	up_write(&mm->mmap_sem);

	return ret;

}
@@ -1030,3 +1039,25 @@ void mpx_notify_unmap(struct mm_struct *mm, struct vm_area_struct *vma, 
	if (ret)

		force_sig(SIGSEGV, current);

}



/* MPX cannot handle addresses above 47 bits yet. */

unsigned long mpx_unmapped_area_check(unsigned long addr, unsigned long len,

		unsigned long flags)

{

	if (!kernel_managing_mpx_tables(current->mm))

		return addr;

	if (addr + len <= DEFAULT_MAP_WINDOW)

		return addr;

	if (flags & MAP_FIXED)

		return -ENOMEM;



	/*

	 * Requested len is larger than the whole area we're allowed to map in.

	 * Resetting hinting address wouldn't do much good -- fail early.

	 */

	if (len > DEFAULT_MAP_WINDOW)

		return -ENOMEM;



	/* Look for unmap area within DEFAULT_MAP_WINDOW */

	return 0;

}

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