netdev - Re: [PATCH net-next v7 2/2] page_pool: Track DMA-mapped pages and unmap them when destroying the pool

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: <87jz7yhix3.fsf@toke.dk>
Date: Sat, 05 Apr 2025 14:50:00 +0200
From: Toke Høiland-Jørgensen <toke@...hat.com>
To: Alexander Lobakin <aleksander.lobakin@...el.com>
Cc: "David S. Miller" <davem@...emloft.net>, Jakub Kicinski
 <kuba@...nel.org>, Jesper Dangaard Brouer <hawk@...nel.org>, Saeed
 Mahameed <saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>, Tariq
 Toukan <tariqt@...dia.com>, Andrew Lunn <andrew+netdev@...n.ch>, Eric
 Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Ilias
 Apalodimas <ilias.apalodimas@...aro.org>, Simon Horman <horms@...nel.org>,
 Andrew Morton <akpm@...ux-foundation.org>, Mina Almasry
 <almasrymina@...gle.com>, Yonglong Liu <liuyonglong@...wei.com>, Yunsheng
 Lin <linyunsheng@...wei.com>, Pavel Begunkov <asml.silence@...il.com>,
 Matthew Wilcox <willy@...radead.org>, netdev@...r.kernel.org,
 bpf@...r.kernel.org, linux-rdma@...r.kernel.org, linux-mm@...ck.org,
 Qiuling Ren <qren@...hat.com>, Yuying Ma <yuma@...hat.com>
Subject: Re: [PATCH net-next v7 2/2] page_pool: Track DMA-mapped pages and
 unmap them when destroying the pool

Alexander Lobakin <aleksander.lobakin@...el.com> writes:

> From: Alexander Lobakin <aleksander.lobakin@...el.com>
> Date: Fri, 4 Apr 2025 17:55:43 +0200
>
>> From: Toke Høiland-Jørgensen <toke@...hat.com>
>> Date: Fri, 04 Apr 2025 12:18:36 +0200
>> 
>>> When enabling DMA mapping in page_pool, pages are kept DMA mapped until
>>> they are released from the pool, to avoid the overhead of re-mapping the
>>> pages every time they are used. This causes resource leaks and/or
>>> crashes when there are pages still outstanding while the device is torn
>>> down, because page_pool will attempt an unmap through a non-existent DMA
>>> device on the subsequent page return.
>> 
>> [...]
>> 
>>> -#define PP_MAGIC_MASK ~0x3UL
>>> +#define PP_MAGIC_MASK ~(PP_DMA_INDEX_MASK | 0x3UL)
>>>  
>>>  /**
>>>   * struct page_pool_params - page pool parameters
>>> @@ -173,10 +212,10 @@ struct page_pool {
>>>  	int cpuid;
>>>  	u32 pages_state_hold_cnt;
>>>  
>>> -	bool has_init_callback:1;	/* slow::init_callback is set */
>>> +	bool dma_sync;			/* Perform DMA sync for device */
>> 
>> Yunsheng said this change to a full bool is redundant in the v6 thread
>> ¯\_(ツ)_/¯

AFAIU, the comment was that the second READ_ONCE() when reading the
field was redundant, because of the rcu_read_lock(). Which may be the
case, but I think keeping it makes the intent of the code clearer. And
in any case, it has nothing to do with changing the type of the field...

-Toke