On Fri, Nov 18, 2022 at 03:20:32PM +0300, Dan Carpenter wrote:
> Hello Ananda,
>
> The patch 9097e28c25c8: "mm: add zblock - new allocator for use via
> zpool API" from Nov 4, 2022, leads to the following Smatch static
> checker warning:
>
> mm/zblock.c:341 zblock_alloc() error: buffer overflow 'block_desc' 29 <= 29 (assuming for loop doesn't break)
> mm/zblock.c:165 cache_insert_block() error: uninitialized symbol 'min_index'.
> mm/zblock.c:412 zblock_reclaim_block() warn: always true condition '(block_type >= 0) => (0-u64max >= 0)'
>
> mm/zblock.c
> 297 static int zblock_alloc(struct zblock_pool *pool, size_t size, gfp_t gfp,
> 298 unsigned long *handle)
> 299 {
> 300 unsigned int block_type, slot;
> 301 struct zblock_block *block;
> 302 struct block_list *list;
> 303
> 304 if (!size)
> 305 return -EINVAL;
> 306
> 307 if (size > PAGE_SIZE)
> 308 return -ENOSPC;
> 309
> 310 /* find basic block type with suitable slot size */
> 311 for (block_type = 0; block_type < ARRAY_SIZE(block_desc); block_type++) {
> 312 if (size <= block_desc[block_type].slot_size)
> 313 break;
> 314 }
>
> "size" is always <= PAGE_SIZE. Is PAGE_SIZE always 4k? If so then this
> code is fine. Smatch is bad at handling arrays.
PAGE_SIZE is 8kB on SPARC/Alpha. It can be 64kB on PPC and ARM. It can
even be 256kB on one of the weirdo architectures (but, honestly, it's
OK if that breaks; it's not well-tested)..
