On 25.06.24 04:48, yskelg@xxxxxxxxx wrote:
> From: Yunseong Kim <yskelg@xxxxxxxxx>
Thank you very much Yunseong, for finding and reporting this potential
null-pointer dereference.
And thank you Markus Elfring for your valuable comments.
>
> A null pointer is stored in the data structure member "path" after a call
> of the function "iucv_path_alloc" failed. This pointer was passed to
> a subsequent call of the function "iucv_path_connect" where an undesirable
> dereference will be performed then. Thus add a corresponding return value
> check. This prevent null pointer dereferenced kernel panic when memory
> exhausted situation with the netiucv driver operating as an FSM state
> in "conn_action_start".
I would prefer an even shorter commit message. Allocating memory
without checking for failure is a common error pattern, I think.
>
> Fixes: eebce3856737 ("[S390]: Adapt netiucv driver to new IUCV API")
> Cc: linux-s390@xxxxxxxxxxxxxxx
> Signed-off-by: Yunseong Kim <yskelg@xxxxxxxxx>
> ---
> drivers/s390/net/netiucv.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/s390/net/netiucv.c b/drivers/s390/net/netiucv.c
> index 039e18d46f76..d3ae78c0240f 100644
> --- a/drivers/s390/net/netiucv.c
> +++ b/drivers/s390/net/netiucv.c
> @@ -855,6 +855,9 @@ static void conn_action_start(fsm_instance *fi, int event, void *arg)
>
> fsm_newstate(fi, CONN_STATE_SETUPWAIT);
> conn->path = iucv_path_alloc(NETIUCV_QUEUELEN_DEFAULT, 0, GFP_KERNEL);
> + if (!conn->path)
> + return;
> +
On 25.06.24 09:24, Markus Elfring wrote:
>
> Would the following statement variant become more appropriate here?
>
> + return -ENOMEM;
conn_action_start(), like the other fsm functions, does not have a return value.
But simply returning will not prevent the next fsm function from trying to use
conn->path.
So I think you need to do
fsm_newstate(fi, CONN_STATE_CONNERR);
before you return.
You could use rc = -ENOMEM and a goto to the IUCV_DBF_TEXT_ debug message,
if you want to. But I am not too concerned about the details of error handling:
If your memory is so scarce that you cannot even allocate a handful of bytes,
then you should be seeing warnings all over the place.
