linux-ext4 - [PATCH 5.4.y 0/1] ext4: fix EXT4_MAX_LOGICAL

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Date:   Tue, 17 Aug 2021 16:12:11 -0500
From:   George Kennedy <george.kennedy@...cle.com>
To:     gregkh@...uxfoundation.org
Cc:     george.kennedy@...cle.com, tytso@....edu, adilger.kernel@...ger.ca,
        stable@...r.kernel.org, dhaval.giani@...cle.com,
        dan.carpenter@...cle.com, linux-ext4@...r.kernel.org,
        riteshh@...ux.ibm.com
Subject: [PATCH 5.4.y 0/1] ext4: fix EXT4_MAX_LOGICAL_BLOCK macro

From: Ritesh Harjani <riteshh@...ux.ibm.com>

ext4 supports max number of logical blocks in a file to be 0xffffffff.
(This is since ext4_extent's ee_block is __le32).
This means that EXT4_MAX_LOGICAL_BLOCK should be 0xfffffffe (starting
from 0 logical offset). This patch fixes this.

The issue was seen when ext4 moved to iomap_fiemap API and when
overlayfs was mounted on top of ext4. Since overlayfs was missing
filemap_check_ranges(), so it could pass a arbitrary huge length which
lead to overflow of map.m_len logic.

This patch fixes that.

Fixes: d3b6f23f7167 ("ext4: move ext4_fiemap to use iomap framework")
Reported-by: syzbot+77fa5bdb65cc39711820@...kaller.appspotmail.com
Signed-off-by: Ritesh Harjani <riteshh@...ux.ibm.com>
Reviewed-by: Jan Kara <jack@...e.cz>
Signed-off-by: Christoph Hellwig <hch@....de>
Link: https://lore.kernel.org/r/20200505154324.3226743-2-hch@lst.de
Signed-off-by: Theodore Ts'o <tytso@....edu>
(cherry picked from commit 175efa81feb8405676e0136d97b10380179c92e0)
Signed-off-by: George Kennedy <george.kennedy@...cle.com>
---
 fs/ext4/ext4.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index bf3eaa9..ae2cb15 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -718,7 +718,7 @@ enum {
 #define EXT4_MAX_BLOCK_FILE_PHYS	0xFFFFFFFF
 
 /* Max logical block we can support */
-#define EXT4_MAX_LOGICAL_BLOCK		0xFFFFFFFF
+#define EXT4_MAX_LOGICAL_BLOCK		0xFFFFFFFE
 
 /*
  * Structure of an inode on the disk
-- 
1.8.3.1