linux-kernel - Re: [PATCH v1] dmaengine: sf-pdma: pdma

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Message-ID: <Y+KVW4o1ZXJHFSZt@spud>
Date:   Tue, 7 Feb 2023 18:15:55 +0000
From:   Conor Dooley <conor@...nel.org>
To:     shravan kumar <shravan.chippa@...rochip.com>, vkoul@...nel.org
Cc:     green.wan@...ive.com, vkoul@...nel.org, palmer@...belt.com,
        paul.walmsley@...ive.com, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org, dmaengine@...r.kernel.org
Subject: Re: [PATCH v1] dmaengine: sf-pdma: pdma_desc memory leak fix

Hey Vinod,

On Fri, Jan 20, 2023 at 03:36:23PM +0530, shravan kumar wrote:
> From: Shravan Chippa <shravan.chippa@...rochip.com>
> 
> Commit b2cc5c465c2c ("dmaengine: sf-pdma: Add multithread support for a
> DMA channel") changed sf_pdma_prep_dma_memcpy() to unconditionally
> allocate a new sf_pdma_desc each time it is called.
> 
> The driver previously recycled descs, by checking the in_use flag, only
> allocating additional descs if the existing one was in use. This logic
> was removed in commit b2cc5c465c2c ("dmaengine: sf-pdma: Add multithread
> support for a DMA channel"), but sf_pdma_free_desc() was not changed to
> handle the new behaviour.
> 
> As a result, each time sf_pdma_prep_dma_memcpy() is called, the previous
> descriptor is leaked, over time leading to memory starvation:
> 
>   unreferenced object 0xffffffe008447300 (size 192):
>   comm "irq/39-mchp_dsc", pid 343, jiffies 4294906910 (age 981.200s)
>   hex dump (first 32 bytes):
>     00 00 00 ff 00 00 00 00 b8 c1 00 00 00 00 00 00  ................
>     00 00 70 08 10 00 00 00 00 00 00 c0 00 00 00 00  ..p.............
>   backtrace:
>     [<00000000064a04f4>] kmemleak_alloc+0x1e/0x28
>     [<00000000018927a7>] kmem_cache_alloc+0x11e/0x178
>     [<000000002aea8d16>] sf_pdma_prep_dma_memcpy+0x40/0x112
> 
> Add the missing kfree() to sf_pdma_free_desc(), and remove the redundant
> in_use flag.
> 
> Fixes: b2cc5c465c2c ("dmaengine: sf-pdma: Add multithread support for a DMA channel")
> Signed-off-by: Shravan Chippa <shravan.chippa@...rochip.com>

Just checking in to make sure that this patch is on your radar.
Is there something you're waiting for on it?

Cheers,
Conor.

> ---
>  drivers/dma/sf-pdma/sf-pdma.c | 3 +--
>  drivers/dma/sf-pdma/sf-pdma.h | 1 -
>  2 files changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/dma/sf-pdma/sf-pdma.c b/drivers/dma/sf-pdma/sf-pdma.c
> index 6b524eb6bcf3..e578ad556949 100644
> --- a/drivers/dma/sf-pdma/sf-pdma.c
> +++ b/drivers/dma/sf-pdma/sf-pdma.c
> @@ -96,7 +96,6 @@ sf_pdma_prep_dma_memcpy(struct dma_chan *dchan,	dma_addr_t dest, dma_addr_t src,
>  	if (!desc)
>  		return NULL;
>  
> -	desc->in_use = true;
>  	desc->dirn = DMA_MEM_TO_MEM;
>  	desc->async_tx = vchan_tx_prep(&chan->vchan, &desc->vdesc, flags);
>  
> @@ -290,7 +289,7 @@ static void sf_pdma_free_desc(struct virt_dma_desc *vdesc)
>  	struct sf_pdma_desc *desc;
>  
>  	desc = to_sf_pdma_desc(vdesc);
> -	desc->in_use = false;
> +	kfree(desc);
>  }
>  
>  static void sf_pdma_donebh_tasklet(struct tasklet_struct *t)
> diff --git a/drivers/dma/sf-pdma/sf-pdma.h b/drivers/dma/sf-pdma/sf-pdma.h
> index dcb3687bd5da..5c398a83b491 100644
> --- a/drivers/dma/sf-pdma/sf-pdma.h
> +++ b/drivers/dma/sf-pdma/sf-pdma.h
> @@ -78,7 +78,6 @@ struct sf_pdma_desc {
>  	u64				src_addr;
>  	struct virt_dma_desc		vdesc;
>  	struct sf_pdma_chan		*chan;
> -	bool				in_use;
>  	enum dma_transfer_direction	dirn;
>  	struct dma_async_tx_descriptor *async_tx;
>  };
> -- 
> 2.34.1
> 

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