[PATCH v4 1/5] nvmem: check invalid number of bytes in nvmem_device_{read,write}

[Biju Das <biju.das@xxxxxxxxxxxxxx>]

Add check in nvmem_device_{read,write}()to ensure that nvmem core never
passes an invalid number of bytes.

Signed-off-by: Biju Das <biju.das@xxxxxxxxxxxxxx>
---
V3-->V4
	* New patch.
---
 drivers/nvmem/core.c | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index d9fd110..db7de33 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -1433,10 +1433,21 @@ int nvmem_device_read(struct nvmem_device *nvmem,
 		      size_t bytes, void *buf)
 {
 	int rc;
+	size_t new_bytes;
 
 	if (!nvmem)
 		return -EINVAL;
 
+	/* Stop the user from reading */
+	if ((offset >= nvmem->size) || (bytes == 0))
+		return 0;
+
+	if (unlikely(check_add_overflow(bytes, offset, &new_bytes)))
+		return -EOVERFLOW;
+
+	if (new_bytes > nvmem->size)
+		bytes = nvmem->size - offset;
+
 	rc = nvmem_reg_read(nvmem, offset, buf, bytes);
 
 	if (rc)
@@ -1461,16 +1472,29 @@ int nvmem_device_write(struct nvmem_device *nvmem,
 		       size_t bytes, void *buf)
 {
 	int rc;
+	size_t new_bytes;
 
 	if (!nvmem)
 		return -EINVAL;
 
+	/* Stop the user from writing */
+	if (offset >= nvmem->size)
+		return -ENOSPC;
+
+	if (bytes == 0)
+		return 0;
+
+	if (unlikely(check_add_overflow(bytes, offset, &new_bytes)))
+		return -EOVERFLOW;
+
+	if (new_bytes > nvmem->size)
+		bytes = nvmem->size - offset;
+
 	rc = nvmem_reg_write(nvmem, offset, buf, bytes);
 
 	if (rc)
 		return rc;
 
-
 	return bytes;
 }
 EXPORT_SYMBOL_GPL(nvmem_device_write);
-- 
2.7.4