2015-12-10 17:29:21

by Alexey Klimov

Subject: [PATCH] mailbox: pcc: fix channel calculation in get_pcc_channel()

This patch fixes the calculation of pcc_chan for non-zero id.
After the compiler ignores the (unsigned long) cast the
pcc_mbox_channels pointer is type-cast and then the type-cast
offset is added which results in address outside of the range
leading to the kernel crashing.

We might add braces and make it:

pcc_chan = (struct mbox_chan *)
((unsigned long) pcc_mbox_channels +
(id * sizeof(*pcc_chan)));

but let's go with array approach here and use id as index.

Tested on Juno board.

Acked-by: Sudeep Holla <[email protected]>
Signed-off-by: Alexey Klimov <[email protected]>
---
drivers/mailbox/pcc.c | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
index 45d85ae..8f779a1 100644
--- a/drivers/mailbox/pcc.c
+++ b/drivers/mailbox/pcc.c
@@ -81,16 +81,10 @@ static struct mbox_controller pcc_mbox_ctrl = {};
*/
static struct mbox_chan *get_pcc_channel(int id)
{
- struct mbox_chan *pcc_chan;
-
if (id < 0 || id > pcc_mbox_ctrl.num_chans)
return ERR_PTR(-ENOENT);

- pcc_chan = (struct mbox_chan *)
- (unsigned long) pcc_mbox_channels +
- (id * sizeof(*pcc_chan));
-
- return pcc_chan;
+ return &pcc_mbox_channels[id];
}

/**
--
1.9.1

2015-12-10 18:19:25

by Ashwin Chaugule

Subject: Re: [PATCH] mailbox: pcc: fix channel calculation in get_pcc_channel()

On 10 December 2015 at 12:28, Alexey Klimov <[email protected]> wrote:
> This patch fixes the calculation of pcc_chan for non-zero id.
> After the compiler ignores the (unsigned long) cast the
> pcc_mbox_channels pointer is type-cast and then the type-cast
> offset is added which results in address outside of the range
> leading to the kernel crashing.
>
> We might add braces and make it:
>
> pcc_chan = (struct mbox_chan *)
> ((unsigned long) pcc_mbox_channels +
> (id * sizeof(*pcc_chan)));
>
> but let's go with array approach here and use id as index.
>
> Tested on Juno board.
>
> Acked-by: Sudeep Holla <[email protected]>
> Signed-off-by: Alexey Klimov <[email protected]>
> ---
> drivers/mailbox/pcc.c | 8 +-------
> 1 file changed, 1 insertion(+), 7 deletions(-)
>
> diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
> index 45d85ae..8f779a1 100644
> --- a/drivers/mailbox/pcc.c
> +++ b/drivers/mailbox/pcc.c
> @@ -81,16 +81,10 @@ static struct mbox_controller pcc_mbox_ctrl = {};
> */
> static struct mbox_chan *get_pcc_channel(int id)
> {
> - struct mbox_chan *pcc_chan;
> -
> if (id < 0 || id > pcc_mbox_ctrl.num_chans)
> return ERR_PTR(-ENOENT);
>
> - pcc_chan = (struct mbox_chan *)
> - (unsigned long) pcc_mbox_channels +
> - (id * sizeof(*pcc_chan));
> -
> - return pcc_chan;
> + return &pcc_mbox_channels[id];
> }
>


Strange that we didn't catch this even with a non-zero id. But the
change makes sense so..

Acked-by: Ashwin Chaugule <[email protected]>

Thanks,
Ashwin.