Re: [RFC PATCH v2] iommu/amd: gray the 'irq_remap_table' object for kmemleak

Michael Wang
2015-11-25T11:15:07Z

Hi, Joery

On 11/20/2015 12:33 PM, Michael Wang wrote:
> The kmemleak testing on 3.18.24 show:
>
> unreferenced object 0xffff880233ff9010 (size 16):
> comm "swapper/0", pid 1, jiffies 4294937440 (age 2010.490s)
> hex dump (first 16 bytes):
> 0a 0a 00 00 20 00 00 00 00 44 fb 33 02 88 ff ff .... ....D.3....
> backtrace:
> [<ffffffff8118192d>] create_object+0x10d/0x2d0
> [<ffffffff815c2d4b>] kmemleak_alloc+0x5b/0xc0
> [<ffffffff8116dd19>] kmem_cache_alloc_trace+0xb9/0x160
> [<ffffffff814ffe51>] get_irq_table+0x151/0x380
>
> This is caused by the 'irq_lookup_table' was allocated with
> __get_free_pages() which won't create kmemleak object, thus it's
> pointers won't be count as referencing 'irq_remap_table' in
> kmemleak scan.
>
> The 'irq_remap_table' won't be freed after initialized, doesn't
> make sense to check it's leaking.
>
> This patch mark the 'irq_remap_table' object as 'gray' to stop
> the 'false positives' report.

Any comments on this one?

Regards,
Michael Wang

>
> Signed-off-by: Michael Wang <yun.wang@profitbricks.com>
> ---
> v2:
> Use kmemleak_not_leak() instead of kmemleak_ignore() since
> the 'irq_remap_table' itself also contain pointer.
>
> drivers/iommu/amd_iommu.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
> index 8b2be1e..87a1a88 100644
> --- a/drivers/iommu/amd_iommu.c
> +++ b/drivers/iommu/amd_iommu.c
> @@ -3603,6 +3603,7 @@ static struct irq_remap_table *get_irq_table(u16 devid, bool ioapic)
> }
>
> irq_lookup_table[devid] = table;
> + kmemleak_not_leak(table);
> set_dte_irq_entry(devid, table);
> iommu_flush_dte(iommu, devid);
> if (devid != alias) {
>