From d3b73ee452bb8d8ad7c96416e08c7ec712220e30 Mon Sep 17 00:00:00 2001
From: Zhang Yi <yi.zhang@huawei.com>
Date: Wed, 8 Sep 2021 20:08:48 +0800
Subject: [PATCH] ext4: check for out-of-order index extents in
 ext4_valid_extent_entries()
Git-commit: 8dd27fecede55e8a4e67eef2878040ecad0f0d33
Patch-mainline: v5.16-rc1
References: bsc#1194163

After commit 5946d089379a ("ext4: check for overlapping extents in
ext4_valid_extent_entries()"), we can check out the overlapping extent
entry in leaf extent blocks. But the out-of-order extent entry in index
extent blocks could also trigger bad things if the filesystem is
inconsistent. So this patch add a check to figure out the out-of-order
index extents and return error.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Link: https://lore.kernel.org/r/20210908120850.4012324-2-yi.zhang@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Acked-by: David Disseldorp <ddiss@suse.de>

---
 fs/ext4/extents.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 3b27eeaa9c1a..ebe2764584b1 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -370,6 +370,9 @@ static int ext4_valid_extent_entries(struct inode *inode,
 				     ext4_fsblk_t *pblk, int depth)
 {
 	unsigned short entries;
+	ext4_lblk_t lblock = 0;
+	ext4_lblk_t prev = 0;
+
 	if (eh->eh_entries == 0)
 		return 1;
 
@@ -378,31 +381,35 @@ static int ext4_valid_extent_entries(struct inode *inode,
 	if (depth == 0) {
 		/* leaf entries */
 		struct ext4_extent *ext = EXT_FIRST_EXTENT(eh);
-		ext4_lblk_t lblock = 0;
-		ext4_lblk_t prev = 0;
-		int len = 0;
 		while (entries) {
 			if (!ext4_valid_extent(inode, ext))
 				return 0;
 
 			/* Check for overlapping extents */
 			lblock = le32_to_cpu(ext->ee_block);
-			len = ext4_ext_get_actual_len(ext);
 			if ((lblock <= prev) && prev) {
 				*pblk = ext4_ext_pblock(ext);
 				return 0;
 			}
+			prev = lblock + ext4_ext_get_actual_len(ext) - 1;
 			ext++;
 			entries--;
-			prev = lblock + len - 1;
 		}
 	} else {
 		struct ext4_extent_idx *ext_idx = EXT_FIRST_INDEX(eh);
 		while (entries) {
 			if (!ext4_valid_extent_idx(inode, ext_idx))
 				return 0;
+
+			/* Check for overlapping index extents */
+			lblock = le32_to_cpu(ext_idx->ei_block);
+			if ((lblock <= prev) && prev) {
+				*pblk = ext4_idx_pblock(ext_idx);
+				return 0;
+			}
 			ext_idx++;
 			entries--;
+			prev = lblock;
 		}
 	}
 	return 1;
-- 
2.34.1