linux-ext4 - [PATCH] ext4: fix signed vs unsigned comparison in ext4_valid

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Message-Id: <20191023013112.18809-1-tytso@mit.edu>
Date:   Tue, 22 Oct 2019 21:31:12 -0400
From:   "Theodore Ts'o" <tytso@....edu>
To:     Ext4 Developers List <linux-ext4@...r.kernel.org>
Cc:     "Theodore Ts'o" <tytso@....edu>, stable@...nel.org
Subject: [PATCH] ext4: fix signed vs unsigned comparison in ext4_valid_extent()

Due to a signed vs unsigned comparison, an invalid extent where
ee_block (the logical block) is so large that lblk + len overflow
wasn't getting flagged as invalid.

As a result, we tripped the BUG_ON(end < lblk) in
ext4_es_cache_extent() when trying to mount a file system with a
corrupted journal inode was corrupted.

https://bugzilla.kernel.org/show_bug.cgi?id=205197

Signed-off-by: Theodore Ts'o <tytso@....edu>
Cc: stable@...nel.org
---
 fs/ext4/extents.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index fb0f99dc8c22..d12bc287abdc 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -367,7 +367,7 @@ ext4_ext_max_entries(struct inode *inode, int depth)
 static int ext4_valid_extent(struct inode *inode, struct ext4_extent *ext)
 {
 	ext4_fsblk_t block = ext4_ext_pblock(ext);
-	int len = ext4_ext_get_actual_len(ext);
+	unsigned int len = ext4_ext_get_actual_len(ext);
 	ext4_lblk_t lblock = le32_to_cpu(ext->ee_block);
 
 	/*
-- 
2.23.0