*
* Safely read from address @src to the buffer at @dst. If a kernel fault
* happens, handle that and return -EFAULT.
+ *
+ * We ensure that the copy_from_user is executed in atomic context so that
+ * do_page_fault() doesn't attempt to take mmap_sem. This makes
+ * probe_kernel_read() suitable for use within regions where the caller
+ * already holds mmap_sem, or other locks which nest inside mmap_sem.
*/
long __weak probe_kernel_read(void *dst, const void *src, size_t size)
pagefault_enable();
set_fs(old_fs);
- return ret < 0 ? ret : src - unsafe_addr;
+ return ret ? -EFAULT : src - unsafe_addr;
}