Re: [PATCH v2] nvmem: core: fix possibly memleak when use nvmem_cell_info_to_nvmem_cell()

Srinivas Kandagatla
2020-09-23T14:10:42Z

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@plvision.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;
>
>