linux-ext4 - [PATCH] ext4: catch integer overflow in ext4_cache

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Date:   Mon, 13 Jul 2020 14:58:18 +0200
From:   Jan Kara <jack@...e.cz>
To:     Ted Tso <tytso@....edu>
Cc:     <linux-ext4@...r.kernel.org>,
        Wolfgang Frisch <wolfgang.frisch@...e.com>,
        Jan Kara <jack@...e.cz>
Subject: [PATCH] ext4: catch integer overflow in ext4_cache_extents

From: Wolfgang Frisch <wolfgang.frisch@...e.com>

When extent tree is corrupted we can hit BUG_ON in
ext4_es_cache_extent(). Check for this and abort caching instead of
crashing the machine.

Signed-off-by: Wolfgang Frisch <wolfgang.frisch@...e.com>
Signed-off-by: Jan Kara <jack@...e.cz>
---
 fs/ext4/extents.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 221f240eae60..e76d00fda104 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -471,6 +471,10 @@ static void ext4_cache_extents(struct inode *inode,
 		ext4_lblk_t lblk = le32_to_cpu(ex->ee_block);
 		int len = ext4_ext_get_actual_len(ex);
 
+		/* Corrupted extent tree? Stop caching... */
+		if (lblk + len < lblk || lblk + len > EXT4_MAX_LOGICAL_BLOCK)
+			return;
+
 		if (prev && (prev != lblk))
 			ext4_es_cache_extent(inode, prev, lblk - prev, ~0,
 					     EXTENT_STATUS_HOLE);
-- 
2.16.4