linux-kernel - Re: [PATCH v3] misc: fastrpc: Fix incorrect DMA mapping unmap request

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Date:   Wed, 2 Aug 2023 14:43:26 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Ekansh Gupta <quic_ekangupt@...cinc.com>,
        linux-arm-msm@...r.kernel.org
Cc:     ekangupt@....qualcomm.com, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org, fastrpc.upstream@....qualcomm.com,
        stable <stable@...nel.org>
Subject: Re: [PATCH v3] misc: fastrpc: Fix incorrect DMA mapping unmap request



On 02/08/2023 06:10, Ekansh Gupta wrote:
> Scatterlist table is obtained during map create request and the same
> table is used for DMA mapping unmap. In case there is any failure
> while getting the sg_table, ERR_PTR is returned instead of sg_table.
> 
> When the map is getting freed, there is only a non-NULL check of
> sg_table which will also be true in case failure was returned instead
> of sg_table. This would result in improper unmap request. Add proper
> check before setting map table to avoid bad unmap request.
> 
> Fixes: c68cfb718c8f ("misc: fastrpc: Add support for context Invoke method")
> Cc: stable <stable@...nel.org>
> Signed-off-by: Ekansh Gupta <quic_ekangupt@...cinc.com>
> ---
> Changes in v2:
>    - Added fixes information to commit text
> Changes in v3:
>    - Set map->table only if attachment for successful
> 
>   drivers/misc/fastrpc.c | 8 +++++---
>   1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index 9666d28..de7c812 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -756,6 +756,7 @@ static int fastrpc_map_create(struct fastrpc_user *fl, int fd,
>   {
>   	struct fastrpc_session_ctx *sess = fl->sctx;
>   	struct fastrpc_map *map = NULL;
> +	struct sg_table *table;
>   	int err = 0;
>   
>   	if (!fastrpc_map_lookup(fl, fd, ppmap, true))
> @@ -783,11 +784,12 @@ static int fastrpc_map_create(struct fastrpc_user *fl, int fd,
>   		goto attach_err;
>   	}
>   
> -	map->table = dma_buf_map_attachment_unlocked(map->attach, DMA_BIDIRECTIONAL);
> -	if (IS_ERR(map->table)) {
> -		err = PTR_ERR(map->table);
> +	table = dma_buf_map_attachment(map->attach, DMA_BIDIRECTIONAL);

Any reason why dma_buf_map_attachment_unlocked changed to 
dma_buf_map_attachment?

--srini
> +	if (IS_ERR(table)) {
> +		err = PTR_ERR(table);
>   		goto map_err;
>   	}
> +	map->table = table;
>   
>   	if (attr & FASTRPC_ATTR_SECUREMAP) {
>   		map->phys = sg_phys(map->table->sgl);