From 57ce0ed4fba064145d497dc901bee4f74cfc5c25 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Thu, 30 Oct 2014 10:52:57 -0400 Subject: [PATCH] ext4: fix overflow when updating superblock backups after resize commit 9378c6768e4fca48971e7b6a9075bc006eda981d upstream. 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 Signed-off-by: Jan Kara Signed-off-by: Theodore Ts'o Reviewed-by: Lukas Czerner Signed-off-by: Greg Kroah-Hartman --- fs/ext4/resize.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c index c503850a61a8..a69bd74ed390 100644 --- a/fs/ext4/resize.c +++ b/fs/ext4/resize.c @@ -1066,7 +1066,7 @@ 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)); -- 2.20.1