Re: ext3/ext4 filesystem corruption under post 5.1.0 kernels

["Theodore Ts'o" <tytso@mit.edu>]

Ah, I think I see the problem.  Sorry, this one was my fault.  Does
this fix things for you?

						- Ted

From 0c72924ef346d54e8627440e6d71257aa5b56105 Mon Sep 17 00:00:00 2001
From: Theodore Ts'o <tytso@mit.edu>
Date: Wed, 15 May 2019 00:51:19 -0400
Subject: [PATCH] ext4: fix block validity checks for journal inodes using indirect blocks

Commit 345c0dbf3a30 ("ext4: protect journal inode's blocks using
block_validity") failed to add an exception for the journal inode in
ext4_check_blockref(), which is the function used by ext4_get_branch()
for indirect blocks.  This caused attempts to read from the ext3-style
journals to fail with:

[  848.968550] EXT4-fs error (device sdb7): ext4_get_branch:171: inode #8: block 30343695: comm jbd2/sdb7-8: invalid block

Fix this by adding the missing exception check.

Fixes: 345c0dbf3a30 ("ext4: protect journal inode's blocks using block_validity")
Reported-by: Arthur Marsh <arthur.marsh@internode.on.net>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
---
 fs/ext4/block_validity.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/ext4/block_validity.c b/fs/ext4/block_validity.c
index 8d03550aaae3..8e83741b02e0 100644
--- a/fs/ext4/block_validity.c
+++ b/fs/ext4/block_validity.c
@@ -277,6 +277,11 @@ int ext4_check_blockref(const char *function, unsigned int line,
 	__le32 *bref = p;
 	unsigned int blk;
 
+	if (ext4_has_feature_journal(inode->i_sb) &&
+	    (inode->i_ino ==
+	     le32_to_cpu(EXT4_SB(inode->i_sb)->s_es->s_journal_inum)))
+		return 0;
+
 	while (bref < p+max) {
 		blk = le32_to_cpu(*bref++);
 		if (blk &&
-- 
2.19.1