linux-kernel - Re: [PATCH] i2c: cp2615: check the return value of kzalloc()

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Message-ID: <CACCVKEFXOKhXmF3rcmKQ8-aMFZJLZOf+imsuBYKAQsWptrJG6Q@mail.gmail.com>
Date:   Sat, 23 Jul 2022 23:01:50 +0200
From:   Bence Csókás <bence98@....bme.hu>
To:     <williamsukatube@....com>
CC:     <linux-i2c@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        William Dean <williamsukatube@...il.com>,
        Hacash Robot <hacashRobot@...tino.com>
Subject: Re: [PATCH] i2c: cp2615: check the return value of kzalloc()

Dear William,
thank you for your insight. However, you will find that the first
access of the variable `msg` is a call to `cp2615_init_iop_msg()`
which, on line 85, checks for the variable being NULL, and if so,
returns -EINVAL, which in turn causes `cp2615_check_iop()` to return
too. In fact, the same mechanism allows for `cp2615_i2c_send()` to
also not have to worry about `kzalloc()` returning NULL.
Though you could argue that in these cases, `cp2615_init_iop_msg()`
should return -ENOMEM instead of -EINVAL, and you would be correct.
Cheers,
Bence


<williamsukatube@....com> ezt írta (időpont: 2022. júl. 23., Szo, 6:33):
>
> From: William Dean <williamsukatube@...il.com>
>
> kzalloc() is a memory allocation function which can return NULL when
> some internal memory errors happen. So it is better to check the
> return value of it to prevent potential wrong memory access or
> memory leak.
>
> Fixes: 4a7695429eade ("i2c: cp2615: add i2c driver for Silicon Labs' CP2615 Digital Audio Bridge")
> Reported-by: Hacash Robot <hacashRobot@...tino.com>
> Signed-off-by: William Dean <williamsukatube@...il.com>
> ---
>  drivers/i2c/busses/i2c-cp2615.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-cp2615.c b/drivers/i2c/busses/i2c-cp2615.c
> index 3ded28632e4c..7c9403346615 100644
> --- a/drivers/i2c/busses/i2c-cp2615.c
> +++ b/drivers/i2c/busses/i2c-cp2615.c
> @@ -171,11 +171,17 @@ cp2615_i2c_recv(struct usb_interface *usbif, unsigned char tag, void *buf)
>  /* Checks if the IOP is functional by querying the part's ID */
>  static int cp2615_check_iop(struct usb_interface *usbif)
>  {
> -       struct cp2615_iop_msg *msg = kzalloc(sizeof(*msg), GFP_KERNEL);
> -       struct cp2615_iop_accessory_info *info = (struct cp2615_iop_accessory_info *)&msg->data;
> +       struct cp2615_iop_msg *msg;
> +       struct cp2615_iop_accessory_info *info;
>         struct usb_device *usbdev = interface_to_usbdev(usbif);
> -       int res = cp2615_init_iop_msg(msg, iop_GetAccessoryInfo, NULL, 0);
> +       int res;
> +
> +       msg = kzalloc(sizeof(*msg), GFP_KERNEL);
> +       if (!msg)
> +               return -ENOMEM;
>
> +       info = (struct cp2615_iop_accessory_info *)&msg->data;
> +       res = cp2615_init_iop_msg(msg, iop_GetAccessoryInfo, NULL, 0);
>         if (res)
>                 goto out;
>
> --
> 2.25.1
>
>