access_ok — Checks if a user space pointer is valid
access_ok ( type, addr, size);
type
Type of access: VERIFY_READ or VERIFY_WRITE. Note that
VERIFY_WRITE is a superset of VERIFY_READ - if it is safe
to write to a block, it is always safe to read from it.
addrUser space pointer to start of block to check
sizeSize of block to check
Checks if a pointer to a block of memory in user space is valid.
Returns true (nonzero) if the memory block may be valid, false (zero) if it is definitely invalid.
Note that, depending on architecture, this function probably just checks that the pointer is in the user space range - after calling this function, memory access functions may still return -EFAULT.