[PATCH 4.9 22/39] ext4: fix fencepost error in check for inode count overflow during resize

From: Greg Kroah-Hartman
Date: Sun Jun 24 2018 - 11:53:29 EST


4.9-stable review patch. If anyone has any objections, please let me know.

------------------

From: Jan Kara <jack@xxxxxxx>

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.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 3f8a6411fbada1fa482276591e037f3b1adcf55b
Reported-by: Jaco Kroon <jaco@xxxxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Reviewed-by: Andreas Dilger <adilger@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
fs/ext4/resize.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -1903,7 +1903,7 @@ 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;
}