The strlen() function returns a size_t which is an unsigned int on 32-bit
arches and an unsigned long on 64-bit arches. But in the drm_copy_field()
function, the strlen() return value is assigned to an 'int len' variable.
Later, the len variable is passed as copy_from_user() third argument that
is an unsigned long parameter as well.
In theory, this can lead to an integer overflow via type conversion. Since
the assignment happens to a signed int lvalue instead of a size_t lvalue.
In practice though, that's unlikely since the values copied are set by DRM
drivers and not controlled by userspace. But using a size_t for len is the
correct thing to do anyways.
Signed-off-by: Javier Martinez Canillas <javierm@xxxxxxxxxx>
Tested-by: Peter Robinson <pbrobinson@xxxxxxxxx>
Reviewed-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
---
Changes in v2:
- Add Peter Robinson Tested-by and Thomas Zimmermann Reviewed-by tags.
drivers/gpu/drm/drm_ioctl.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index 8faad23dc1d8..e1b9a03e619c 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -472,7 +472,7 @@ EXPORT_SYMBOL(drm_invalid_op);
*/
static int drm_copy_field(char __user *buf, size_t *buf_len, const char *value)
{
- int len;
+ size_t len;
/* don't overflow userbuf */
len = strlen(value);
--
2.36.1
