linux-kernel - [PATCH] ext4: eliminate bogus error in ext4_data_block_valid

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Message-ID: <20210703230555.4093-1-trdgn@amazon.com>
Date:   Sat, 3 Jul 2021 16:05:55 -0700
From:   Tahsin Erdogan <trdgn@...zon.com>
To:     Jan Kara <jack@...e.cz>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     Tahsin Erdogan <trdgn@...zon.com>, <stable@...r.kernel.org>,
        Theodore Ts'o <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        <linux-ext4@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] ext4: eliminate bogus error in ext4_data_block_valid_rcu()

Mainline commit ce9f24cccdc0 ("ext4: check journal inode extents more carefully")
enabled validity checks for journal inode's data blocks. This change got
ported to stable branches, but the backport for 4.19 has a bug where it will
flag an error even when system block entry's inode number matches journal
inode.

The way error is reported is also problematic because it updates the superblock
without following journaling rules. This may result in superblock checksum
errors if the superblock is in the process of being committed but has a
previously calculated checksum that doesn't include the bogus error update.

This patch eliminates the bogus error by trying to match how other backports
were implemented, which is to flag an error only when inode numbers mismatch.

Fixes: commit a75a5d163857 ("ext4: check journal inode extents more carefully")
Signed-off-by: Tahsin Erdogan <trdgn@...zon.com>
Cc: stable@...r.kernel.org
Cc: Jan Kara <jack@...e.cz>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/ext4/block_validity.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/block_validity.c b/fs/ext4/block_validity.c
index 1ea8fc9ff048..1bc65ecd4bd6 100644
--- a/fs/ext4/block_validity.c
+++ b/fs/ext4/block_validity.c
@@ -171,8 +171,10 @@ static int ext4_data_block_valid_rcu(struct ext4_sb_info *sbi,
 		else if (start_blk >= (entry->start_blk + entry->count))
 			n = n->rb_right;
 		else {
+			if (entry->ino == ino)
+				return 1;
 			sbi->s_es->s_last_error_block = cpu_to_le64(start_blk);
-			return entry->ino == ino;
+			return 0;
 		}
 	}
 	return 1;
-- 
2.17.1