commit c9b528c35795b711331ed36dc3dbee90d5812d4e upstream.
This mostly reverts commit 6bd97bf273bd ("ext4: remove redundant
mb_regenerate_buddy()") and reintroduces mb_regenerate_buddy(). Based on
code in mb_free_blocks(), fast commit replay can end up marking as free
blocks that are already marked as such. This causes corruption of the
buddy bitmap so we need to regenerate it in that case.
Reported-by: Jan Kara <jack@xxxxxxx>
Fixes: 6bd97bf273bd ("ext4: remove redundant mb_regenerate_buddy()")
CVE: CVE-2024-26601
Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Link: https://lore.kernel.org/r/20240104142040.2835097-4-libaokun1@xxxxxxxxxx
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>
---
fs/ext4/mballoc.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 762c2f8b5b2a..63e4c3b9e608 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -1168,6 +1168,24 @@ void ext4_mb_generate_buddy(struct super_block *sb,
mb_update_avg_fragment_size(sb, grp);
}
+static void mb_regenerate_buddy(struct ext4_buddy *e4b)
+{
+ int count;
+ int order = 1;
+ void *buddy;
+
+ while ((buddy = mb_find_buddy(e4b, order++, &count)))
+ ext4_set_bits(buddy, 0, count);
+
+ e4b->bd_info->bb_fragments = 0;
+ memset(e4b->bd_info->bb_counters, 0,
+ sizeof(*e4b->bd_info->bb_counters) *
+ (e4b->bd_sb->s_blocksize_bits + 2));
+
+ ext4_mb_generate_buddy(e4b->bd_sb, e4b->bd_buddy,
+ e4b->bd_bitmap, e4b->bd_group, e4b->bd_info);
+}
+
/* The buddy information is attached the buddy cache inode
* for convenience. The information regarding each group
* is loaded via ext4_mb_load_buddy. The information involve
@@ -1846,6 +1864,8 @@ static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b,
ext4_mark_group_bitmap_corrupted(
sb, e4b->bd_group,
EXT4_GROUP_INFO_BBITMAP_CORRUPT);
+ } else {
+ mb_regenerate_buddy(e4b);
}
goto done;
}
--
2.31.1
