[PATCH 3.16 088/366] ext4: fix fencepost error in check for inode count overflow during resize

Ben Hutchings
2018-11-11T20:13:17Z

From: Jan Kara <jack@suse.cz>

commit 4f2f76f751433908364ccff82f437a57d0e6e9b7 upstream.

ext4_resize_fs() has an off-by-one bug when checking whether growing of
a filesystem will not overflow inode count. As a result it allows a
filesystem with 8192 inodes per group to grow to 64TB which overflows
inode count to 0 and makes filesystem unusable. Fix it.

Fixes: 3f8a6411fbada1fa482276591e037f3b1adcf55b
Reported-by: Jaco Kroon <jaco@uls.co.za>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/ext4/resize.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -1906,7 +1906,7 @@ retry:
return 0;

n_group = ext4_get_group_number(sb, n_blocks_count - 1);
- if (n_group > (0xFFFFFFFFUL / EXT4_INODES_PER_GROUP(sb))) {
+ if (n_group >= (0xFFFFFFFFUL / EXT4_INODES_PER_GROUP(sb))) {
ext4_warning(sb, "resize would cause inodes_count overflow");
return -EINVAL;
}