[PATCH v3] iommu/io-pgtable-arm-v7s: Add error handle for page table allocation failure

[Robin Murphy]

On 2021-12-07 11:33, yf.wang at mediatek.com wrote:
> From: Yunfei Wang <yf.wang at mediatek.com>
> 
> In __arm_v7s_alloc_table function:
> iommu call kmem_cache_alloc to allocate page table, this function
> allocate memory may fail, when kmem_cache_alloc fails to allocate
> table, call virt_to_phys will be abnomal and return unexpected phys
> and goto out_free, then call kmem_cache_free to release table will
> trigger KE, __get_free_pages and free_pages have similar problem,
> so add error handle for page table allocation failure.
> 
> Fixes: 29859aeb8a6ea ("iommu/io-pgtable-arm-v7s: Abort allocation when table address overflows the PTE")
> Signed-off-by: Yunfei Wang <yf.wang at mediatek.com>
> Cc: <stable at vger.kernel.org> # 5.10.*

Is this genuinely a realistic issue which distro users can hit? In 
practice, a system that can't allocate 2KB is already dead and almost 
certainly isn't coming back either way.

Still, v3 has managed to address my other review comments before I'd 
even finished writing them, so for the change itself,

Acked-by: Robin Murphy <robin.murphy at arm.com>

Thanks,
Robin.

> ---
> v3: Update patch
>      1. Remove unnecessary log print as suggested by Will.
>      2. Remove unnecessary condition check.
> v2: Cc stable at vger.kernel.org
>      1. This patch needs to be merged stable branch, add stable at vger.kernel.org
>         in mail list.
>      2. There is No new code change in v2.
> 
> ---
>   drivers/iommu/io-pgtable-arm-v7s.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/io-pgtable-arm-v7s.c b/drivers/iommu/io-pgtable-arm-v7s.c
> index bfb6acb651e5..be066c1503d3 100644
> --- a/drivers/iommu/io-pgtable-arm-v7s.c
> +++ b/drivers/iommu/io-pgtable-arm-v7s.c
> @@ -246,13 +246,17 @@ static void *__arm_v7s_alloc_table(int lvl, gfp_t gfp,
>   			__GFP_ZERO | ARM_V7S_TABLE_GFP_DMA, get_order(size));
>   	else if (lvl == 2)
>   		table = kmem_cache_zalloc(data->l2_tables, gfp);
> +
> +	if (!table)
> +		return NULL;
> +
>   	phys = virt_to_phys(table);
>   	if (phys != (arm_v7s_iopte)phys) {
>   		/* Doesn't fit in PTE */
>   		dev_err(dev, "Page table does not fit in PTE: %pa", &phys);
>   		goto out_free;
>   	}
> -	if (table && !cfg->coherent_walk) {
> +	if (!cfg->coherent_walk) {
>   		dma = dma_map_single(dev, table, size, DMA_TO_DEVICE);
>   		if (dma_mapping_error(dev, dma))
>   			goto out_free;
>