fs/exec.c: move ->recursion_depth out of critical sections

->recursion_depth is changed only by current, therefore decrementing can
be done without taking any locks.

Link: http://lkml.kernel.org/r/20190417213150.GA26474@avx2Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/exec.c

@@ -1652,11 +1652,13 @@ int search_binary_handler(struct linux_binprm *bprm)
 		if (!try_module_get(fmt->module))
 			continue;
 		read_unlock(&binfmt_lock);
+
 		bprm->recursion_depth++;
 		retval = fmt->load_binary(bprm);
+		bprm->recursion_depth--;
+
 		read_lock(&binfmt_lock);
 		put_binfmt(fmt);
-		bprm->recursion_depth--;
 		if (retval < 0 && !bprm->mm) {
 			/* we got to flush_old_exec() and failed after it */
 			read_unlock(&binfmt_lock);