linux-ext4 - [RFC 6/6] ext4: Add extra check in ext4_mb_mark_bb() to prevent against possible corruption

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Message-Id: <fa6d3adad7e1a4691c4c38b6b670d9330757ce82.1643642105.git.riteshh@linux.ibm.com>
Date:   Mon, 31 Jan 2022 20:46:55 +0530
From:   Ritesh Harjani <riteshh@...ux.ibm.com>
To:     linux-ext4@...r.kernel.org
Cc:     linux-fsdevel@...r.kernel.org, "Theodore Ts'o" <tytso@....edu>,
        Jan Kara <jack@...e.cz>,
        Harshad Shirwadkar <harshadshirwadkar@...il.com>,
        Ritesh Harjani <riteshh@...ux.ibm.com>
Subject: [RFC 6/6] ext4: Add extra check in ext4_mb_mark_bb() to prevent against possible corruption

This patch adds an extra checks in ext4_mb_mark_bb() function
to make sure we mark & report error if we were to mark/clear any
of the critical FS metadata specific bitmaps (&bail out) to prevent
from any accidental corruption.

Signed-off-by: Ritesh Harjani <riteshh@...ux.ibm.com>
---
 fs/ext4/mballoc.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 5f20e355d08c..c94888534caa 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -3920,6 +3920,13 @@ void ext4_mb_mark_bb(struct super_block *sb, ext4_fsblk_t block,
 		len -= overflow;
 	}
 
+	if (!ext4_group_block_valid(sb, group, block, len)) {
+		ext4_error(sb, "Marking blocks in system zone - "
+			   "Block = %llu, len = %d", block, len);
+		bitmap_bh = NULL;
+		goto out_err;
+	}
+
 	clen = EXT4_NUM_B2C(sbi, len);
 
 	bitmap_bh = ext4_read_block_bitmap(sb, group);
-- 
2.31.1