From: Steven Price <steven.price@arm.com>
To: Kangjie Lu <kjlu@umn.edu>
Cc: pakki001@umn.edu, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
Sudeep Holla <sudeep.holla@arm.com>
Subject: Re: [PATCH] firmware: arm_scmi: check return value of idr_find
Date: Mon, 25 Mar 2019 11:54:58 +0000 [thread overview]
Message-ID: <225abd6e-4551-213d-367b-93d938789188@arm.com> (raw)
In-Reply-To: <20190309040239.32431-1-kjlu@umn.edu>
On 09/03/2019 04:02, Kangjie Lu wrote:
> idr_find may return NULL, so check its return value and return an
> error code.
>
> Signed-off-by: Kangjie Lu <kjlu@umn.edu>
> ---
> drivers/firmware/arm_scmi/driver.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
> index 8f952f2f1a29..35faa203d549 100644
> --- a/drivers/firmware/arm_scmi/driver.c
> +++ b/drivers/firmware/arm_scmi/driver.c
> @@ -709,6 +709,8 @@ scmi_mbox_chan_setup(struct scmi_info *info, struct device *dev, int prot_id)
>
> if (scmi_mailbox_check(np)) {
> cinfo = idr_find(&info->tx_idr, SCMI_PROTOCOL_BASE);
> + if (!cinfo)
> + return -EINVAL;
> goto idr_alloc;
> }
>
>
I don't believe this situation can ever actually occur. The
SCMI_PROTOCOL_BASE id is reserved just after the IDR is created in
scmi_probe() in the first call to scmi_mbox_chan_setup(). That first
call can't enter the above if() block because the scmi_mailbox_check()
call has already been checked in scmi_probe(). It is only when
processing the children in subsequent calls to scmi_mbox_chan_setup()
that the check is on another node and so might fail. But by this time
the SCMI_PROTOCOL_BASE id must exist.
So there shouldn't be any way of reaching the situation where the IDR
doesn't contain SCMI_PROTOCOL_BASE and idr_find() returns NULL.
Having said that it did take me a while to understand the code well
enough to reason that, and the above return should be handled
appropriately, so you can add my Reviewed-by. But it would be worth
expanding the commit message pointing out that there isn't actually a
bug (yet).
Steve
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next prev parent reply other threads:[~2019-03-25 11:55 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-09 4:02 [PATCH] firmware: arm_scmi: check return value of idr_find Kangjie Lu
2019-03-23 2:18 ` Kangjie Lu
2019-03-25 11:54 ` Steven Price [this message]
2019-03-25 20:48 ` Kangjie Lu
2019-03-26 11:34 ` Steven Price
2019-04-10 16:31 ` Sudeep Holla
2019-04-10 16:25 ` Sudeep Holla
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