Re: [PATCH] firmware: edd: fix a NULL pointer dereference

[Johannes Thumshirn]

On 23/03/2019 23:10, Kangjie Lu wrote:
> As other functions in this module do, edev should be checked to
> ensure that it is not NULL.
> The fix inserts such as check to avoid potential NULL pointer
> dereference.
> 
> Signed-off-by: Kangjie Lu 
> ---
>  drivers/firmware/edd.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/firmware/edd.c b/drivers/firmware/edd.c
> index 1b82c89a49df..7ebfaca53721 100644
> --- a/drivers/firmware/edd.c
> +++ b/drivers/firmware/edd.c
> @@ -279,6 +279,8 @@ static ssize_t
>  edd_show_mbr_signature(struct edd_device *edev, char *buf)
>  {
>   char *p = buf;
> + if (!edev)
> + return -EINVAL;


I don't think this can ever be NULL.

edd_show_mbr_signature() is called from edd_attr_show(), which
simplified looks like this:

define to_edd_device(obj) container_of(obj,struct edd_device,kobj)

edd_attr_show(struct kobject * kobj, struct attribute *attr, char *buf)
{
struct edd_device *dev = to_edd_device(kobj);
[...]

if (edd_attr->show)
ret = edd_attr->show(dev, buf);
[...]
}

The edd_device structure has the kobject embedded, otherwise the up-cast
won't work.

Byte,
Johannes
-- 
Johannes ThumshirnSUSE Labs Filesystems
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[PATCH] firmware: edd: fix a NULL pointer dereference

[Kangjie Lu]

As other functions in this module do, edev should be checked to
ensure that it is not NULL.
The fix inserts such as check to avoid potential NULL pointer
dereference.

Signed-off-by: Kangjie Lu 
---
 drivers/firmware/edd.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/firmware/edd.c b/drivers/firmware/edd.c
index 1b82c89a49df..7ebfaca53721 100644
--- a/drivers/firmware/edd.c
+++ b/drivers/firmware/edd.c
@@ -279,6 +279,8 @@ static ssize_t
 edd_show_mbr_signature(struct edd_device *edev, char *buf)
 {
char *p = buf;
+   if (!edev)
+   return -EINVAL;
p += scnprintf(p, left, "0x%08x\n", edev->mbr_signature);
return (p - buf);
 }
-- 
2.17.1