From ec298b958cb0c40d70c68079da933c8f31c5134c Mon Sep 17 00:00:00 2001
From: Kent Overstreet <kent.overstreet@gmail.com>
Date: Fri, 12 Feb 2021 20:11:25 -0500
Subject: [PATCH] lib/generic-radix-tree.c: Don't overflow in peek()

[ Upstream commit 9492261ff2460252cf2d8de89cdf854c7e2b28a0 ]

When we started spreading new inode numbers throughout most of the 64
bit inode space, that triggered some corner case bugs, in particular
some integer overflows related to the radix tree code. Oops.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/linux/generic-radix-tree.h |  7 +++++++
 lib/generic-radix-tree.c           | 17 ++++++++++++++---
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/include/linux/generic-radix-tree.h b/include/linux/generic-radix-tree.h
index 107613f7d792..f6cd0f909d9f 100644
--- a/include/linux/generic-radix-tree.h
+++ b/include/linux/generic-radix-tree.h
@@ -38,6 +38,7 @@
 
 #include <asm/page.h>
 #include <linux/bug.h>
+#include <linux/limits.h>
 #include <linux/log2.h>
 #include <linux/math.h>
 #include <linux/types.h>
@@ -184,6 +185,12 @@ void *__genradix_iter_peek(struct genradix_iter *, struct __genradix *, size_t);
 static inline void __genradix_iter_advance(struct genradix_iter *iter,
 					   size_t obj_size)
 {
+	if (iter->offset + obj_size < iter->offset) {
+		iter->offset	= SIZE_MAX;
+		iter->pos	= SIZE_MAX;
+		return;
+	}
+
 	iter->offset += obj_size;
 
 	if (!is_power_of_2(obj_size) &&
diff --git a/lib/generic-radix-tree.c b/lib/generic-radix-tree.c
index f25eb111c051..7dfa88282b00 100644
--- a/lib/generic-radix-tree.c
+++ b/lib/generic-radix-tree.c
@@ -166,6 +166,10 @@ void *__genradix_iter_peek(struct genradix_iter *iter,
 	struct genradix_root *r;
 	struct genradix_node *n;
 	unsigned level, i;
+
+	if (iter->offset == SIZE_MAX)
+		return NULL;
+
 restart:
 	r = READ_ONCE(radix->root);
 	if (!r)
@@ -184,10 +188,17 @@ restart:
 			(GENRADIX_ARY - 1);
 
 		while (!n->children[i]) {
+			size_t objs_per_ptr = genradix_depth_size(level);
+
+			if (iter->offset + objs_per_ptr < iter->offset) {
+				iter->offset	= SIZE_MAX;
+				iter->pos	= SIZE_MAX;
+				return NULL;
+			}
+
 			i++;
-			iter->offset = round_down(iter->offset +
-					   genradix_depth_size(level),
-					   genradix_depth_size(level));
+			iter->offset = round_down(iter->offset + objs_per_ptr,
+						  objs_per_ptr);
 			iter->pos = (iter->offset >> PAGE_SHIFT) *
 				objs_per_page;
 			if (i == GENRADIX_ARY)