include/wrapper/uaccess.h

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * wrapper/uaccess.h
   4  *
   5  * wrapper around linux/uaccess.h.
   6  *
   7  * Copyright (C) 2019 Michael Jeanson <mjeanson@efficios.com>
   8  */
   9
  10 #ifndef _LTTNG_WRAPPER_UACCESS_H
  11 #define _LTTNG_WRAPPER_UACCESS_H
  12
  13 #include <linux/uaccess.h>
  14 #include <wrapper/bitops.h>
  15 #include <lttng/kernel-version.h>
  16
  17 #if (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,0,0) || \
  18         LTTNG_RHEL_KERNEL_RANGE(4,18,0,147,0,0, 4,19,0,0,0,0))
  19
  20 #define VERIFY_READ     0
  21 #define VERIFY_WRITE    1
  22 #define lttng_access_ok(type, addr, size) access_ok(addr, size)
  23
  24 #else /* LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,0,0) */
  25
  26 #define lttng_access_ok(type, addr, size) access_ok(type, addr, size)
  27
  28 #endif /* LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,0,0) */
  29
  30 #if LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,4,0)
  31 static __always_inline __must_check int
  32 lttng_copy_struct_from_user(void *dst, size_t ksize, const void __user *src,
  33                       size_t usize)
  34 {
  35         return copy_struct_from_user(dst, ksize, src, usize);
  36 }
  37 #else /* LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,4,0) */
  38 /**
  39  * lttng_check_zeroed_user: check if a userspace buffer only contains zero bytes
  40  * @from: Source address, in userspace.
  41  * @size: Size of buffer.
  42  *
  43  * This is effectively shorthand for "memchr_inv(from, 0, size) == NULL" for
  44  * userspace addresses (and is more efficient because we don't care where the
  45  * first non-zero byte is).
  46  *
  47  * Returns:
  48  *  * 0: There were non-zero bytes present in the buffer.
  49  *  * 1: The buffer was full of zero bytes.
  50  *  * -EFAULT: access to userspace failed.
  51  */
  52 static inline
  53 int lttng_check_zeroed_user(const void __user *from, size_t size)
  54 {
  55         unsigned long val;
  56         uintptr_t align = (uintptr_t) from % sizeof(unsigned long);
  57         int ret;
  58
  59         if (unlikely(size == 0))
  60                 return 1;
  61
  62         from -= align;
  63         size += align;
  64
  65         if (!lttng_access_ok(VERIFY_READ, from, size))
  66                 return -EFAULT;
  67
  68         ret = get_user(val, (unsigned long __user *) from);
  69         if (ret)
  70                 return ret;
  71         if (align)
  72                 val &= ~lttng_aligned_byte_mask(align);
  73
  74         while (size > sizeof(unsigned long)) {
  75                 if (unlikely(val))
  76                         goto done;
  77
  78                 from += sizeof(unsigned long);
  79                 size -= sizeof(unsigned long);
  80
  81                 ret = get_user(val, (unsigned long __user *) from);
  82                 if (ret)
  83                         return ret;
  84         }
  85
  86         if (size < sizeof(unsigned long))
  87                 val &= lttng_aligned_byte_mask(size);
  88
  89 done:
  90         return (val == 0);
  91 }
  92
  93 static __always_inline __must_check int
  94 lttng_copy_struct_from_user(void *dst, size_t ksize, const void __user *src,
  95                       size_t usize)
  96 {
  97         size_t size = min(ksize, usize);
  98         size_t rest = max(ksize, usize) - size;
  99
 100         /* Deal with trailing bytes. */
 101         if (usize < ksize) {
 102                 memset(dst + size, 0, rest);
 103         } else if (usize > ksize) {
 104                 int ret = lttng_check_zeroed_user(src + size, rest);
 105                 if (ret <= 0)
 106                         return ret ?: -E2BIG;
 107         }
 108         /* Copy the interoperable parts of the struct. */
 109         if (copy_from_user(dst, src, size))
 110                 return -EFAULT;
 111         return 0;
 112 }
 113 #endif /* LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,4,0) */
 114
 115 #endif /* _LTTNG_WRAPPER_UACCESS_H */