netdev - Re: [PATCH net] ice: Add check for kzalloc

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Date:   Tue, 6 Dec 2022 10:47:01 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Jiasheng Jiang <jiasheng@...as.ac.cn>
Cc:     jesse.brandeburg@...el.com, anthony.l.nguyen@...el.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, intel-wired-lan@...ts.osuosl.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] ice: Add check for kzalloc

Tue, Dec 06, 2022 at 04:08:05AM CET, jiasheng@...as.ac.cn wrote:
>As kzalloc may fail and return NULL pointer,
>it should be better to check the return value
>in order to avoid the NULL pointer dereference.

Okay, so? Be imperative to the code base, tell it what to do in your
patch description.


>
>Fixes: d6b98c8d242a ("ice: add write functionality for GNSS TTY")
>Signed-off-by: Jiasheng Jiang <jiasheng@...as.ac.cn>
>---
> drivers/net/ethernet/intel/ice/ice_gnss.c | 13 ++++++++++++-
> 1 file changed, 12 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/net/ethernet/intel/ice/ice_gnss.c b/drivers/net/ethernet/intel/ice/ice_gnss.c
>index b5a7f246d230..6d3d5e75726b 100644
>--- a/drivers/net/ethernet/intel/ice/ice_gnss.c
>+++ b/drivers/net/ethernet/intel/ice/ice_gnss.c
>@@ -421,7 +421,7 @@ static struct tty_driver *ice_gnss_create_tty_driver(struct ice_pf *pf)
> 	const int ICE_TTYDRV_NAME_MAX = 14;
> 	struct tty_driver *tty_driver;
> 	char *ttydrv_name;
>-	unsigned int i;
>+	unsigned int i, j;
> 	int err;
> 
> 	tty_driver = tty_alloc_driver(ICE_GNSS_TTY_MINOR_DEVICES,
>@@ -462,6 +462,17 @@ static struct tty_driver *ice_gnss_create_tty_driver(struct ice_pf *pf)
> 					       GFP_KERNEL);
> 		pf->gnss_serial[i] = NULL;
> 
>+		if (!pf->gnss_tty_port[i]) {
>+			for (j = 0; j < i; j++) {
>+				tty_port_destroy(pf->gnss_tty_port[j]);

You are destroying port which you didn't call (pf->gnss_tty_port[i])
for. Also, you are introducing a code duplication here with the error
path couple of lines below. Please convert this to goto-label error
path so the cleanup code is shared.


>+				kfree(pf->gnss_tty_port[j]);
>+			}
>+			kfree(ttydrv_name);
>+			tty_driver_kref_put(pf->ice_gnss_tty_driver);
>+
>+			return NULL;
>+		}
>+
> 		tty_port_init(pf->gnss_tty_port[i]);
> 		tty_port_link_device(pf->gnss_tty_port[i], tty_driver, i);
> 	}
>-- 
>2.25.1
>