lib/usercopy.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/bitops.h>
   3 #include <linux/fault-inject-usercopy.h>
   4 #include <linux/instrumented.h>
   5 #include <linux/uaccess.h>
   6
   7 /* out-of-line parts */
   8
   9 #ifndef INLINE_COPY_FROM_USER
  10 unsigned long _copy_from_user(void *to, const void __user *from, unsigned long n)
  11 {
  12         unsigned long res = n;
  13         might_fault();
  14         if (!should_fail_usercopy() && likely(access_ok(from, n))) {
  15                 instrument_copy_from_user(to, from, n);
  16                 res = raw_copy_from_user(to, from, n);
  17         }
  18         if (unlikely(res))
  19                 memset(to + (n - res), 0, res);
  20         return res;
  21 }
  22 EXPORT_SYMBOL(_copy_from_user);
  23 #endif
  24
  25 #ifndef INLINE_COPY_TO_USER
  26 unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n)
  27 {
  28         might_fault();
  29         if (should_fail_usercopy())
  30                 return n;
  31         if (likely(access_ok(to, n))) {
  32                 instrument_copy_to_user(to, from, n);
  33                 n = raw_copy_to_user(to, from, n);
  34         }
  35         return n;
  36 }
  37 EXPORT_SYMBOL(_copy_to_user);
  38 #endif
  39
  40 /**
  41  * check_zeroed_user: check if a userspace buffer only contains zero bytes
  42  * @from: Source address, in userspace.
  43  * @size: Size of buffer.
  44  *
  45  * This is effectively shorthand for "memchr_inv(from, 0, size) == NULL" for
  46  * userspace addresses (and is more efficient because we don't care where the
  47  * first non-zero byte is).
  48  *
  49  * Returns:
  50  *  * 0: There were non-zero bytes present in the buffer.
  51  *  * 1: The buffer was full of zero bytes.
  52  *  * -EFAULT: access to userspace failed.
  53  */
  54 int check_zeroed_user(const void __user *from, size_t size)
  55 {
  56         unsigned long val;
  57         uintptr_t align = (uintptr_t) from % sizeof(unsigned long);
  58
  59         if (unlikely(size == 0))
  60                 return 1;
  61
  62         from -= align;
  63         size += align;
  64
  65         if (!user_read_access_begin(from, size))
  66                 return -EFAULT;
  67
  68         unsafe_get_user(val, (unsigned long __user *) from, err_fault);
  69         if (align)
  70                 val &= ~aligned_byte_mask(align);
  71
  72         while (size > sizeof(unsigned long)) {
  73                 if (unlikely(val))
  74                         goto done;
  75
  76                 from += sizeof(unsigned long);
  77                 size -= sizeof(unsigned long);
  78
  79                 unsafe_get_user(val, (unsigned long __user *) from, err_fault);
  80         }
  81
  82         if (size < sizeof(unsigned long))
  83                 val &= aligned_byte_mask(size);
  84
  85 done:
  86         user_read_access_end();
  87         return (val == 0);
  88 err_fault:
  89         user_read_access_end();
  90         return -EFAULT;
  91 }
  92 EXPORT_SYMBOL(check_zeroed_user);