Source of usercopy.c - linux-imx - PHYTEC BitBucket (Stash)

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        /* Verify object does not incorrectly span multiple pages. */
        check_page_span(ptr, n, page, to_user);
    }
}
​
static DEFINE_STATIC_KEY_FALSE_RO(bypass_usercopy_checks);
​
/*
 * Validates that the given object is:
 * - not bogus address
 * - known-safe heap or stack object
 * - fully contained by stack (or stack frame, when available)
 * - fully within SLAB object (or object whitelist area, when available)
 * - not in kernel text
 */
void __check_object_size(const void *ptr, unsigned long n, bool to_user)
{
    if (static_branch_unlikely(&bypass_usercopy_checks))
        return;
​
    /* Skip all tests if size is zero. */
    if (!n)
        return;
​
    /* Check for invalid addresses. */
    check_bogus_address((const unsigned long)ptr, n, to_user);
​
    /* Check for bad heap object. */
    check_heap_object(ptr, n, to_user);
​
    /* Check for bad stack object. */
    switch (check_stack_object(ptr, n)) {
    case NOT_STACK:
        /* Object is not touching the current process stack. */
        break;
    case GOOD_FRAME:
    case GOOD_STACK:
        /*
         * Object is either in the correct frame (when it
         * is possible to check) or just generally on the
         * process stack (when frame checking not available).
         */
        return;
    default:
        usercopy_abort("process stack", NULL, to_user, 0, n);
    }
​
    /* Check for bad heap object. */
    check_heap_object(ptr, n, to_user);
​
    /* Check for object in kernel to avoid text exposure. */
    check_kernel_text_object((const unsigned long)ptr, n, to_user);
}
EXPORT_SYMBOL(__check_object_size);
​
static bool enable_checks __initdata = true;
​
static int __init parse_hardened_usercopy(char *str)
{
    return strtobool(str, &enable_checks);