gfs2: Always check inode size of inline inodes

Check if the inode size of stuffed (inline) inodes is within the allowed
range when reading inodes from disk (gfs2_dinode_in()).  This prevents
us from on-disk corruption.

The two checks in stuffed_readpage() and gfs2_unstuffer_page() that just
truncate inline data to the maximum allowed size don't actually make
sense, and they can be removed now as well.

Reported-by: syzbot+7bb81dfa9cda07d9cd9d@syzkaller.appspotmail.com
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

fs/gfs2/aops.c

@@ -427,8 +427,6 @@ static int stuffed_readpage(struct gfs2_inode *ip, struct page *page)
 		return error;
 
 	kaddr = kmap_atomic(page);
-	if (dsize > gfs2_max_stuffed_size(ip))
-		dsize = gfs2_max_stuffed_size(ip);
 	memcpy(kaddr, dibh->b_data + sizeof(struct gfs2_dinode), dsize);
 	memset(kaddr + dsize, 0, PAGE_SIZE - dsize);
 	kunmap_atomic(kaddr);

fs/gfs2/bmap.c

@@ -61,9 +61,6 @@ static int gfs2_unstuffer_page(struct gfs2_inode *ip, struct buffer_head *dibh,
 		void *kaddr = kmap(page);
 		u64 dsize = i_size_read(inode);
  
-		if (dsize > gfs2_max_stuffed_size(ip))
-			dsize = gfs2_max_stuffed_size(ip);
-
 		memcpy(kaddr, dibh->b_data + sizeof(struct gfs2_dinode), dsize);
 		memset(kaddr + dsize, 0, PAGE_SIZE - dsize);
 		kunmap(page);

fs/gfs2/glops.c

@@ -449,6 +449,9 @@ static int gfs2_dinode_in(struct gfs2_inode *ip, const void *buf)
 	ip->i_depth = (u8)depth;
 	ip->i_entries = be32_to_cpu(str->di_entries);
 
+	if (gfs2_is_stuffed(ip) && inode->i_size > gfs2_max_stuffed_size(ip))
+		goto corrupt;
+
 	if (S_ISREG(inode->i_mode))
 		gfs2_set_aops(inode);