linux-ext4 - [PATCH 1/5] ext4: Fix EXT4_MAX_LOGICAL

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Message-Id: <e31dbabc453d1f227371bed6e0cc2f3493b4955f.1587555962.git.riteshh@linux.ibm.com>
Date:   Thu, 23 Apr 2020 16:17:53 +0530
From:   Ritesh Harjani <riteshh@...ux.ibm.com>
To:     linux-ext4@...r.kernel.org
Cc:     jack@...e.cz, tytso@....edu, adilger@...ger.ca,
        darrick.wong@...cle.com, hch@...radead.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Ritesh Harjani <riteshh@...ux.ibm.com>,
        Murphy Zhou <jencce.kernel@...il.com>,
        Miklos Szeredi <miklos@...redi.hu>,
        Amir Goldstein <amir73il@...il.com>,
        linux-fsdevel@...r.kernel.org, linux-unionfs@...r.kernel.org,
        syzbot+77fa5bdb65cc39711820@...kaller.appspotmail.com
Subject: [PATCH 1/5] ext4: Fix EXT4_MAX_LOGICAL_BLOCK macro

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>
---
 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 91eb4381cae5..ad2dbf6e4924 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -722,7 +722,7 @@ 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
-- 
2.21.0