9063c61fd5
The discussion about using "access_ok()" in get_user_pages_fast() (see
commit 7f81890687: "x86: don't use
'access_ok()' as a range check in get_user_pages_fast()" for details and
end result), made us notice that x86-64 was really being very sloppy
about virtual address checking.
So be way more careful and straightforward about masking x86-64 virtual
addresses:
- All the VIRTUAL_MASK* variants now cover half of the address
space, it's not like we can use the full mask on a signed
integer, and the larger mask just invites mistakes when
applying it to either half of the 48-bit address space.
- /proc/kcore's kc_offset_to_vaddr() becomes a lot more
obvious when it transforms a file offset into a
(kernel-half) virtual address.
- Unify/simplify the 32-bit and 64-bit USER_DS definition to
be based on TASK_SIZE_MAX.
This cleanup and more careful/obvious user virtual address checking also
uncovered a buglet in the x86-64 implementation of strnlen_user(): it
would do an "access_ok()" check on the whole potential area, even if the
string itself was much shorter, and thus return an error even for valid
strings. Our sloppy checking had hidden this.
So this fixes 'strnlen_user()' to do this properly, the same way we
already handled user strings in 'strncpy_from_user()'. Namely by just
checking the first byte, and then relying on fault handling for the
rest. That always works, since we impose a guard page that cannot be
mapped at the end of the user space address space (and even if we
didn't, we'd have the address space hole).
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
76 lines
2.2 KiB
C
76 lines
2.2 KiB
C
#ifndef _ASM_X86_PAGE_64_DEFS_H
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#define _ASM_X86_PAGE_64_DEFS_H
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#define THREAD_ORDER 1
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#define THREAD_SIZE (PAGE_SIZE << THREAD_ORDER)
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#define CURRENT_MASK (~(THREAD_SIZE - 1))
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#define EXCEPTION_STACK_ORDER 0
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#define EXCEPTION_STKSZ (PAGE_SIZE << EXCEPTION_STACK_ORDER)
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#define DEBUG_STACK_ORDER (EXCEPTION_STACK_ORDER + 1)
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#define DEBUG_STKSZ (PAGE_SIZE << DEBUG_STACK_ORDER)
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#define IRQ_STACK_ORDER 2
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#define IRQ_STACK_SIZE (PAGE_SIZE << IRQ_STACK_ORDER)
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#define STACKFAULT_STACK 1
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#define DOUBLEFAULT_STACK 2
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#define NMI_STACK 3
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#define DEBUG_STACK 4
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#define MCE_STACK 5
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#define N_EXCEPTION_STACKS 5 /* hw limit: 7 */
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#define PUD_PAGE_SIZE (_AC(1, UL) << PUD_SHIFT)
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#define PUD_PAGE_MASK (~(PUD_PAGE_SIZE-1))
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/*
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* Set __PAGE_OFFSET to the most negative possible address +
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* PGDIR_SIZE*16 (pgd slot 272). The gap is to allow a space for a
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* hypervisor to fit. Choosing 16 slots here is arbitrary, but it's
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* what Xen requires.
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*/
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#define __PAGE_OFFSET _AC(0xffff880000000000, UL)
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#define __PHYSICAL_START ((CONFIG_PHYSICAL_START + \
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(CONFIG_PHYSICAL_ALIGN - 1)) & \
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~(CONFIG_PHYSICAL_ALIGN - 1))
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#define __START_KERNEL (__START_KERNEL_map + __PHYSICAL_START)
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#define __START_KERNEL_map _AC(0xffffffff80000000, UL)
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/* See Documentation/x86/x86_64/mm.txt for a description of the memory map. */
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#define __PHYSICAL_MASK_SHIFT 46
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#define __VIRTUAL_MASK_SHIFT 47
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/*
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* Kernel image size is limited to 512 MB (see level2_kernel_pgt in
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* arch/x86/kernel/head_64.S), and it is mapped here:
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*/
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#define KERNEL_IMAGE_SIZE (512 * 1024 * 1024)
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#define KERNEL_IMAGE_START _AC(0xffffffff80000000, UL)
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#ifndef __ASSEMBLY__
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void clear_page(void *page);
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void copy_page(void *to, void *from);
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/* duplicated to the one in bootmem.h */
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extern unsigned long max_pfn;
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extern unsigned long phys_base;
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extern unsigned long __phys_addr(unsigned long);
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#define __phys_reloc_hide(x) (x)
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#define vmemmap ((struct page *)VMEMMAP_START)
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extern void init_extra_mapping_uc(unsigned long phys, unsigned long size);
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extern void init_extra_mapping_wb(unsigned long phys, unsigned long size);
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#endif /* !__ASSEMBLY__ */
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#ifdef CONFIG_FLATMEM
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#define pfn_valid(pfn) ((pfn) < max_pfn)
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#endif
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#endif /* _ASM_X86_PAGE_64_DEFS_H */
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