ext4: add sanity checking to count_overhead() (c48ae41b) · Commits · 戴 / test

The commit "ext4: sanity check the block and cluster size at mount time" should prevent any problems, but in case the superblock is modified while the file system is mounted, add an extra safety check to make sure we won't overrun the allocated buffer. Signed-off-by:

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

fs/ext4/super.c

+8 −3

Original line number	Diff line number	Diff line
		@@ -3195,10 +3195,15 @@ static int count_overhead(struct super_block *sb, ext4_group_t grp,
		ext4_set_bit(s++, buf);
		count++;
		}
		for (j = ext4_bg_num_gdb(sb, grp); j > 0; j--) {
		j = ext4_bg_num_gdb(sb, grp);
		if (s + j > EXT4_BLOCKS_PER_GROUP(sb)) {
		ext4_error(sb, "Invalid number of block group "
		"descriptor blocks: %d", j);
		j = EXT4_BLOCKS_PER_GROUP(sb) - s;
		}
		count += j;
		for (; j > 0; j--)
		ext4_set_bit(EXT4_B2C(sbi, s++), buf);
		count++;
		}
		}
		if (!count)
		return 0;

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