Re: [bug report] reimplement IDR and IDA using the radix tree

[Dan Carpenter <dan.carpenter@oracle.com>]

@linux.intel.com is bouncing my emails again...  This happened some
years back as well.

On Thu, Dec 08, 2016 at 02:56:51PM +0300, Dan Carpenter wrote:
> Hello Matthew Wilcox,
> 
> This is a semi-automatic email about new static checker warnings.
> 
> The patch 755edccbffa1: "reimplement IDR and IDA using the radix 
> tree" from Dec 7, 2016, leads to the following Smatch complaint:
> 
> lib/radix-tree.c:2380 ida_get_new_above()
> 	 warn: variable dereferenced before check 'node' (see line 2355)
> 
> lib/radix-tree.c
>   2354			bit = 0;
>   2355		offset = get_slot_offset(node, slot);
>                                          ^^^^
> Dereferenced inside the function.
> 
>   2356	
>   2357		bitmap = *slot;
>   2358		if (bitmap) {
>   2359			bit = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, bit);
>   2360			index += bit;
>   2361			if (index > INT_MAX)
>   2362				return -ENOSPC;
>   2363			if (bit = IDA_BITMAP_BITS) {
>   2364				index /= IDA_BITMAP_BITS;
>   2365				goto restart;
>   2366			}
>   2367			__set_bit(bit, bitmap->bitmap);
>   2368			if (bitmap_full(bitmap->bitmap, IDA_BITMAP_BITS))
>   2369				node_tag_clear(root, node, IDR_FREE, offset);
>   2370			bitmap = xchg(&ida->free_bitmap, NULL);
>   2371			kfree(bitmap);
>   2372		} else {
>   2373			index += bit;
>   2374			bitmap = xchg(&ida->free_bitmap, NULL);
>   2375			if (!bitmap)
>   2376				return -EAGAIN;
>   2377			memset(bitmap, 0, sizeof(*bitmap));
>   2378			__set_bit(bit, bitmap->bitmap);
>   2379			rcu_assign_pointer(*slot, bitmap);
>   2380			if (node)
>                             ^^^^
> Check too late.
> 
>   2381				node->count++;
>   2382		}
> 
> regards,
> dan carpenter