Re: [PATCH] nvmem: core: add sanity check in nvmem_device_read()

From: Srinivas Kandagatla
Date: Tue Aug 04 2020 - 06:03:31 EST

On 04/08/2020 10:58, Sakari Ailus wrote:
Hi Bingbu,

Thank you for the patch.

On Tue, Aug 04, 2020 at 05:13:56PM +0800, Bingbu Cao wrote:
nvmem_device_read() could be called directly once nvmem device
registered, the sanity check should be done before call
nvmem_reg_read() as cell and sysfs read did now.

Signed-off-by: Bingbu Cao <bingbu.cao@xxxxxxxxx>
drivers/nvmem/core.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index 927eb5f6003f..c9a77993f008 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -1491,6 +1491,13 @@ int nvmem_device_read(struct nvmem_device *nvmem,
if (!nvmem)
return -EINVAL;
+ if (offset >= nvmem->size || bytes < nvmem->word_size)
+ return 0;
+ if (bytes + offset > nvmem->size)
+ bytes = nvmem->size - offset;

The check is relevant for nvmem_device_write(), too.

There are also other ways to access nvmem devices such as nvmem_cell_read
and others alike. Should they be considered as well?

We should probably move these sanity checks to a common place like nvmem_reg_read() and nvmem_reg_write(), so the callers need not duplicate the same!


+ bytes = round_down(bytes, nvmem->word_size);
rc = nvmem_reg_read(nvmem, offset, buf, bytes);
if (rc)