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

Vadym Kochan
2020-09-23T14:13:48Z

On Wed, Sep 23, 2020 at 03:10:36PM +0100, Srinivas Kandagatla wrote:
>
>
> 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 :-)
>
But what about nvmem_device_cell_{read,write} case ?
In my understanding the cell is allocated on the stack but kstrdup() is
not freed in the end, or I missed something ?

>
> 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;
> >