ext4: fix false negatives *and* false positives in ext4_check_descriptors() (44de022c) · Commits · 戴 / test

Ext4_check_descriptors() was getting called before s_gdb_count was initialized. So for file systems w/o the meta_bg feature, allocation bitmaps could overlap the block group descriptors and ext4 wouldn't notice. For file systems with the meta_bg feature enabled, there was a fencepost error which would cause the ext4_check_descriptors() to incorrectly believe that the block allocation bitmap overlaps with the block group descriptor blocks, and it would reject the mount. Fix both of these problems. Signed-off-by:

Theodore Ts'o <tytso@mit.edu> Cc: stable@vger.kernel.org

fs/ext4/super.c

+2 −3

Original line number	Diff line number	Diff line
		@@ -2342,7 +2342,7 @@ static int ext4_check_descriptors(struct super_block *sb,
		struct ext4_sb_info *sbi = EXT4_SB(sb);
		ext4_fsblk_t first_block = le32_to_cpu(sbi->s_es->s_first_data_block);
		ext4_fsblk_t last_block;
		ext4_fsblk_t last_bg_block = sb_block + ext4_bg_num_gdb(sb, 0) + 1;
		ext4_fsblk_t last_bg_block = sb_block + ext4_bg_num_gdb(sb, 0);
		ext4_fsblk_t block_bitmap;
		ext4_fsblk_t inode_bitmap;
		ext4_fsblk_t inode_table;
		@@ -4085,14 +4085,13 @@ static int ext4_fill_super(struct super_block sb, void data, int silent)
		goto failed_mount2;
		}
		}
		sbi->s_gdb_count = db_count;
		if (!ext4_check_descriptors(sb, logical_sb_block, &first_not_zeroed)) {
		ext4_msg(sb, KERN_ERR, "group descriptors corrupted!");
		ret = -EFSCORRUPTED;
		goto failed_mount2;
		}

		sbi->s_gdb_count = db_count;

		timer_setup(&sbi->s_err_report, print_daily_error_info, 0);

		/* Register extent status tree shrinker */

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