linux-kernel - Re: [PATCH v2 2/2] dma-buf: system_heap: account for system heap allocation in memcg

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <7a0fcf24-09de-4f6e-8a0b-7b631b1315bb@amd.com>
Date: Wed, 14 Jan 2026 11:38:27 +0100
From: Christian König <christian.koenig@....com>
To: Eric Chanudet <echanude@...hat.com>,
 Sumit Semwal <sumit.semwal@...aro.org>,
 Benjamin Gaignard <benjamin.gaignard@...labora.com>,
 Brian Starkey <Brian.Starkey@....com>, John Stultz <jstultz@...gle.com>,
 "T.J. Mercier" <tjmercier@...gle.com>, Maxime Ripard <mripard@...hat.com>
Cc: linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] dma-buf: system_heap: account for system heap
 allocation in memcg

On 1/13/26 22:32, Eric Chanudet wrote:
> The system dma-buf heap lets userspace allocate buffers from the page
> allocator. However, these allocations are not accounted for in memcg,
> allowing processes to escape limits that may be configured.
> 
> Pass __GFP_ACCOUNT for system heap allocations, based on the
> dma_heap.mem_accounting parameter, to use memcg and account for them.
> 
> Signed-off-by: Eric Chanudet <echanude@...hat.com>
> ---
>  drivers/dma-buf/heaps/system_heap.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
> index 4c782fe33fd497a74eb5065797259576f9b651b6..139b50df64ed4c4a6fdd69f25fe48324fbe2c481 100644
> --- a/drivers/dma-buf/heaps/system_heap.c
> +++ b/drivers/dma-buf/heaps/system_heap.c
> @@ -52,6 +52,8 @@ static gfp_t order_flags[] = {HIGH_ORDER_GFP, HIGH_ORDER_GFP, LOW_ORDER_GFP};
>  static const unsigned int orders[] = {8, 4, 0};
>  #define NUM_ORDERS ARRAY_SIZE(orders)
>  
> +extern bool mem_accounting;

Please define that in some header. Apart from that looks good technically.

But after the discussion it sounds more and more like we don't want to account device driver allocated memory in memcg at all.

Regards,
Christian.

> +
>  static int dup_sg_table(struct sg_table *from, struct sg_table *to)
>  {
>  	struct scatterlist *sg, *new_sg;
> @@ -320,14 +322,17 @@ static struct page *alloc_largest_available(unsigned long size,
>  {
>  	struct page *page;
>  	int i;
> +	gfp_t flags;
>  
>  	for (i = 0; i < NUM_ORDERS; i++) {
>  		if (size <  (PAGE_SIZE << orders[i]))
>  			continue;
>  		if (max_order < orders[i])
>  			continue;
> -
> -		page = alloc_pages(order_flags[i], orders[i]);
> +		flags = order_flags[i];
> +		if (mem_accounting)
> +			flags |= __GFP_ACCOUNT;
> +		page = alloc_pages(flags, orders[i]);
>  		if (!page)
>  			continue;
>  		return page;
>