quota: check block number when reading the block in quota file

The block number in the quota tree on disk should be smaller than the
v2_disk_dqinfo.dqi_blocks. If the quota file was corrupted, we may be
allocating an 'allocated' block and that would lead to a loop in a tree,
which will probably trigger oops later. This patch adds a check for the
block number in the quota tree to prevent such potential issue.

Link: https://lore.kernel.org/r/20211008093821.1001186-2-yi.zhang@huawei.com
Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Cc: stable@kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>

diff --git a/fs/quota/quota_tree.c b/fs/quota/quota_tree.c
index d3e995e..583b7f7 100644 (file)
--- a/fs/quota/quota_tree.c
+++ b/fs/quota/quota_tree.c
@@ -479,6 +479,13 @@ static int remove_tree(struct qtree_mem_dqinfo *info, struct dquot *dquot,
                goto out_buf;
        }
        newblk = le32_to_cpu(ref[get_index(info, dquot->dq_id, depth)]);
+       if (newblk < QT_TREEOFF || newblk >= info->dqi_blocks) {
+               quota_error(dquot->dq_sb, "Getting block too big (%u >= %u)",
+                           newblk, info->dqi_blocks);
+               ret = -EUCLEAN;
+               goto out_buf;
+       }
+
        if (depth == info->dqi_qtree_depth - 1) {
                ret = free_dqentry(info, dquot, newblk);
                newblk = 0;
@@ -578,6 +585,13 @@ static loff_t find_tree_dqentry(struct qtree_mem_dqinfo *info,
        blk = le32_to_cpu(ref[get_index(info, dquot->dq_id, depth)]);
        if (!blk)       /* No reference? */
                goto out_buf;
+       if (blk < QT_TREEOFF || blk >= info->dqi_blocks) {
+               quota_error(dquot->dq_sb, "Getting block too big (%u >= %u)",
+                           blk, info->dqi_blocks);
+               ret = -EUCLEAN;
+               goto out_buf;
+       }
+
        if (depth < info->dqi_qtree_depth - 1)
                ret = find_tree_dqentry(info, dquot, blk, depth+1);
        else