linux-kernel - Re: [PATCH v2] nvmem: core: fix possibly memleak when use nvmem_cell_info_to_nvmem

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Date:   Wed, 23 Sep 2020 15:10:36 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Vadym Kochan <vadym.kochan@...ision.eu>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] nvmem: core: fix possibly memleak when use
 nvmem_cell_info_to_nvmem_cell()



On 23/09/2020 14:53, Vadym Kochan wrote:
> Fix missing 'kfree_const(cell->name)' when call to
> nvmem_cell_info_to_nvmem_cell() in several places:
> 
>       * after nvmem_cell_info_to_nvmem_cell() failed during
>         nvmem_add_cells()
> 
>       * during nvmem_device_cell_{read,write}. This is fixed by simply
>         re-using info->name instead of duplicating it:
> 
>             cell->name = info->name
> 
> Because cell->name is not used except for error message printing in case
> of un-aligned access, the new __nvmem_cell_info_to_nvmem_cell() helper
> was introduced.
> 
> Fixes: e2a5402ec7c6 ("nvmem: Add nvmem_device based consumer apis.")
> Signed-off-by: Vadym Kochan <vadym.kochan@...ision.eu>
> ---
> v2:
>      * remove not needed 'kfree_const(cell->name)' after nvmem_cell_info_to_nvmem_cell()
>        failed.
> 
>   drivers/nvmem/core.c | 35 ++++++++++++++++++++++++++---------
>   1 file changed, 26 insertions(+), 9 deletions(-)



Really :-)


Below change should just fix this the reported issue!
------------------------>cut<---------------------------

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index 6cd3edb2eaf6..9fb9112fe75d 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -383,6 +383,7 @@ static int nvmem_cell_info_to_nvmem_cell(struct 
nvmem_device *nvmem,
                 dev_err(&nvmem->dev,
                         "cell %s unaligned to nvmem stride %d\n",
                         cell->name, nvmem->stride);
+               kfree_const(cell->name);
                 return -EINVAL;
         }

------------------------>cut<---------------------------

I don't see a point in the way your patch try to fix this!!


--srini

> 
> diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
> index 6cd3edb2eaf6..e6d1bc414faf 100644
> --- a/drivers/nvmem/core.c
> +++ b/drivers/nvmem/core.c
> @@ -361,16 +361,15 @@ static void nvmem_cell_add(struct nvmem_cell *cell)
>   	blocking_notifier_call_chain(&nvmem_notifier, NVMEM_CELL_ADD, cell);
>   }
>   
> -static int nvmem_cell_info_to_nvmem_cell(struct nvmem_device *nvmem,
> -				   const struct nvmem_cell_info *info,
> -				   struct nvmem_cell *cell)
> +static int
> +__nvmem_cell_info_to_nvmem_cell(struct nvmem_device *nvmem,
> +				const struct nvmem_cell_info *info,
> +				struct nvmem_cell *cell)
>   {
>   	cell->nvmem = nvmem;
>   	cell->offset = info->offset;
>   	cell->bytes = info->bytes;
> -	cell->name = kstrdup_const(info->name, GFP_KERNEL);
> -	if (!cell->name)
> -		return -ENOMEM;
> +	cell->name = info->name;
>   
>   	cell->bit_offset = info->bit_offset;
>   	cell->nbits = info->nbits;
> @@ -382,13 +381,31 @@ static int nvmem_cell_info_to_nvmem_cell(struct nvmem_device *nvmem,
>   	if (!IS_ALIGNED(cell->offset, nvmem->stride)) {
>   		dev_err(&nvmem->dev,
>   			"cell %s unaligned to nvmem stride %d\n",
> -			cell->name, nvmem->stride);
> +			cell->name ?: "<unknown>", nvmem->stride);
>   		return -EINVAL;
>   	}
>   
>   	return 0;
>   }
>   
> +static int
> +nvmem_cell_info_to_nvmem_cell(struct nvmem_device *nvmem,
> +			      const struct nvmem_cell_info *info,
> +			      struct nvmem_cell *cell)
> +{
> +	int err;
> +
> +	err = __nvmem_cell_info_to_nvmem_cell(nvmem, info, cell);
> +	if (err)
> +		return err;
> +
> +	cell->name = kstrdup_const(info->name, GFP_KERNEL);
> +	if (!cell->name)
> +		return -ENOMEM;
> +
> +	return 0;
> +}
> +
>   /**
>    * nvmem_add_cells() - Add cell information to an nvmem device
>    *
> @@ -1460,7 +1477,7 @@ ssize_t nvmem_device_cell_read(struct nvmem_device *nvmem,
>   	if (!nvmem)
>   		return -EINVAL;
>   
> -	rc = nvmem_cell_info_to_nvmem_cell(nvmem, info, &cell);
> +	rc = __nvmem_cell_info_to_nvmem_cell(nvmem, info, &cell);
>   	if (rc)
>   		return rc;
>   
> @@ -1490,7 +1507,7 @@ int nvmem_device_cell_write(struct nvmem_device *nvmem,
>   	if (!nvmem)
>   		return -EINVAL;
>   
> -	rc = nvmem_cell_info_to_nvmem_cell(nvmem, info, &cell);
> +	rc = __nvmem_cell_info_to_nvmem_cell(nvmem, info, &cell);
>   	if (rc)
>   		return rc;
>   
>