quota: Sanity-check quota file headers on load

Perform basic sanity checks of quota headers to avoid kernel crashes on
corrupted quota files.

CC: stable@vger.kernel.org
Reported-by: syzbot+f816042a7ae2225f25ba@syzkaller.appspotmail.com
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: Jan Kara <jack@suse.cz>

diff --git a/fs/quota/quota_v2.c b/fs/quota/quota_v2.c
index e69a2bf..c211065 100644 (file)
--- a/fs/quota/quota_v2.c
+++ b/fs/quota/quota_v2.c
@@ -157,6 +157,25 @@ static int v2_read_file_info(struct super_block *sb, int type)
                qinfo->dqi_entry_size = sizeof(struct v2r1_disk_dqblk);
                qinfo->dqi_ops = &v2r1_qtree_ops;
        }
+       ret = -EUCLEAN;
+       /* Some sanity checks of the read headers... */
+       if ((loff_t)qinfo->dqi_blocks << qinfo->dqi_blocksize_bits >
+           i_size_read(sb_dqopt(sb)->files[type])) {
+               quota_error(sb, "Number of blocks too big for quota file size (%llu > %llu).",
+                   (loff_t)qinfo->dqi_blocks << qinfo->dqi_blocksize_bits,
+                   i_size_read(sb_dqopt(sb)->files[type]));
+               goto out;
+       }
+       if (qinfo->dqi_free_blk >= qinfo->dqi_blocks) {
+               quota_error(sb, "Free block number too big (%u >= %u).",
+                           qinfo->dqi_free_blk, qinfo->dqi_blocks);
+               goto out;
+       }
+       if (qinfo->dqi_free_entry >= qinfo->dqi_blocks) {
+               quota_error(sb, "Block with free entry too big (%u >= %u).",
+                           qinfo->dqi_free_entry, qinfo->dqi_blocks);
+               goto out;
+       }
        ret = 0;
 out:
        up_read(&dqopt->dqio_sem);