Commit 9378c676 authored Oct 30, 2014 by Jan Kara Committed by Theodore Ts'o Oct 30, 2014

ext4: fix overflow when updating superblock backups after resize



When there are no meta block groups update_backups() will compute the
backup block in 32-bit arithmetics thus possibly overflowing the block
number and corrupting the filesystem. OTOH filesystems without meta
block groups larger than 16 TB should be rare. Fix the problem by doing
the counting in 64-bit arithmetics.

Coverity-id: 741252
CC: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Lukas Czerner <lczerner@redhat.com>

parent cac7f242

fs/ext4/resize.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1081,7 +1081,7 @@ static void update_backups(struct super_block sb, int blk_off, char data,
		break;

		if (meta_bg == 0)
		backup_block = group * bpg + blk_off;
		backup_block = ((ext4_fsblk_t)group) * bpg + blk_off;
		else
		backup_block = (ext4_group_first_block_no(sb, group) +
		ext4_bg_has_super(sb, group));

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