efdc1e2083
Instead of doing byte-at-a-time user accesses to figure out where the fault occurred, read the saved fault_address from the current thread structure. For the sake of defensive programming, if the fault_address does not fall into the user buffer range, simply assume the whole area faulted. This will cause the fixup for copy_from_user() to clear the entire kernel side buffer. Signed-off-by: David S. Miller <davem@davemloft.net>
66 lines
1.6 KiB
C
66 lines
1.6 KiB
C
/* user_fixup.c: Fix up user copy faults.
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*
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* Copyright (C) 2004 David S. Miller <davem@redhat.com>
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*/
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#include <linux/compiler.h>
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#include <linux/kernel.h>
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#include <linux/string.h>
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#include <linux/errno.h>
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#include <asm/uaccess.h>
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/* Calculating the exact fault address when using
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* block loads and stores can be very complicated.
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*
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* Instead of trying to be clever and handling all
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* of the cases, just fix things up simply here.
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*/
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static unsigned long compute_size(unsigned long start, unsigned long size, unsigned long *offset)
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{
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unsigned long fault_addr = current_thread_info()->fault_address;
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unsigned long end = start + size;
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if (fault_addr < start || fault_addr >= end) {
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*offset = 0;
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} else {
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*offset = start - fault_addr;
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size = end - fault_addr;
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}
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return size;
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}
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unsigned long copy_from_user_fixup(void *to, const void __user *from, unsigned long size)
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{
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unsigned long offset;
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size = compute_size((unsigned long) from, size, &offset);
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if (likely(size))
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memset(to + offset, 0, size);
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return size;
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}
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unsigned long copy_to_user_fixup(void __user *to, const void *from, unsigned long size)
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{
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unsigned long offset;
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return compute_size((unsigned long) to, size, &offset);
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}
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unsigned long copy_in_user_fixup(void __user *to, void __user *from, unsigned long size)
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{
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unsigned long fault_addr = current_thread_info()->fault_address;
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unsigned long start = (unsigned long) to;
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unsigned long end = start + size;
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if (fault_addr >= start && fault_addr < end)
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return end - fault_addr;
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start = (unsigned long) from;
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end = start + size;
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if (fault_addr >= start && fault_addr < end)
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return end - fault_addr;
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return size;
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}
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