Linux Driver Verification » Linux Kernel Safety RuleDB

SUMMARY¶

All allocated memory in a pool should be freed before destroying the pool.

DESCRIPTION¶

Adherence to this rule prevents possible driver errors related to release of memory regions, which are still being used.

Memory pools are released by calling `dma_pool_destroy(struct dma_pool* pool)` or `pci_pool_destroy(struct pci_pool* pool)` functions. However, before memory pools can be released, the memory in them should be deallocated.

Therefore, for each pool, all memory regions allocated by `dma_pool_alloc()` or `pci_pool_alloc()` should be released by `dma_pool_free()` or `pci_pool_free()` before the appropriate `destroy` function is applied to the pool in subject.

EXAMPLE
Correct usage example:¶

int some_kernel_ehci_module_func(/*non-important data type*/ ehci) {
struct ehci_qtd *qtd;
dma_addr_t dma;

ehci->qtd_pool = pci_pool_create ("ehci_qtd", ehci->hcd.pdev,
sizeof (struct ehci_qtd),
32 /* byte alignment /,
4096 / can't cross 4K */,
flags);
if (!ehci->qtd_pool) {
//Some error handling!
}

//Some non-important code stuff

qtd = pci_pool_alloc (ehci->qtd_pool, flags, &dma);
//Simple trying to alloc some memory portion from our pci-pool

if (qtd != 0) {
memset (qtd, 0, sizeof *qtd);
qtd->qtd_dma = dma; //Working with allocated structure data
qtd->hw_next = EHCI_LIST_END; //With another one...
qtd->hw_alt_next = EHCI_LIST_END;
INIT_LIST_HEAD (&qtd->qtd_list);
}

//Here, we need to free our allocated memory portion,
//because pci-pool need to be destroyed

pci_pool_free (ehci->qtd_pool, qtd, qtd->qtd_dma);

//Now, if all is OK, we can destroy our pci-pool

if (ehci->qtd_pool)
pci_pool_destroy (ehci->qtd_pool);
ehci->qtd_pool = 0;
}