linux-kernel - Re: [PATCH v2 1/7] i2c: npcm: restore slave addresses array length

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Message-ID: <CACD3sJbAYwiXrapgBDrtwNfVLr-109zExMrktunui6HKxtO-OQ@mail.gmail.com>
Date: Fri, 6 Sep 2024 10:23:40 +0800
From: Tyrone Ting <warp5tw@...il.com>
To: Andi Shyti <andi.shyti@...nel.org>
Cc: avifishman70@...il.com, tmaimon77@...il.com, tali.perry1@...il.com, 
	venture@...gle.com, yuenn@...gle.com, benjaminfair@...gle.com, 
	andriy.shevchenko@...ux.intel.com, wsa@...nel.org, rand.sec96@...il.com, 
	wsa+renesas@...g-engineering.com, tali.perry@...oton.com, 
	Avi.Fishman@...oton.com, tomer.maimon@...oton.com, KWLIU@...oton.com, 
	JJLIU0@...oton.com, kfting@...oton.com, openbmc@...ts.ozlabs.org, 
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/7] i2c: npcm: restore slave addresses array length

Hi Andi:

Thank you for your review.

Andi Shyti <andi.shyti@...nel.org> 於 2024年9月6日 週五 上午5:24寫道：
>
> Hi Tyrone,
>
> On Fri, Aug 30, 2024 at 11:46:34AM GMT, Tyrone Ting wrote:
> > The smatch check warning is "buffer overflow 'npcm_i2caddr' 2 <= 9".
> > The original design supports 10 slave addresses although only 2
>
> please remember that the "slave" term has been replaced by the
> "target" term. I will change it when applying the patch.
>

Thank you for your reminder. I'll change the term ever since.

> > addresses are required for current implementation.
> >
> > Restore the npcm_i2caddr array length to fix the smatch warning.
> >
> > Fixes: 47d506d1a28f ("i2c: npcm: Remove own slave addresses 2:10")
>
> I don't think the Fixes tag is necessary here. This change is
> primarily addressing a static analyzer warning. While some cases
> come close to a buffer overflow, it couldn’t have occurred in
> practice since we don't actually have the devices listed in
> npcm_i2caddr[].
>

Understood. I'll remove the Fixes tag.

> > Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
> > Closes: https://lore.kernel.org/r/202408130818.FgDP5uNm-lkp@intel.com/
> > Signed-off-by: Tyrone Ting <kfting@...oton.com>
> > ---
> >  drivers/i2c/busses/i2c-npcm7xx.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
> > index 2fe68615942e..bbcb4d6668ce 100644
> > --- a/drivers/i2c/busses/i2c-npcm7xx.c
> > +++ b/drivers/i2c/busses/i2c-npcm7xx.c
> > @@ -136,11 +136,13 @@ enum i2c_addr {
> >   * Since the addr regs are sprinkled all over the address space,
> >   * use this array to get the address or each register.
> >   */
> > -#define I2C_NUM_OWN_ADDR 2
> > +#define I2C_NUM_OWN_ADDR 10
> >  #define I2C_NUM_OWN_ADDR_SUPPORTED 2
> >
> >  static const int npcm_i2caddr[I2C_NUM_OWN_ADDR] = {
> > -     NPCM_I2CADDR1, NPCM_I2CADDR2,
> > +     NPCM_I2CADDR1, NPCM_I2CADDR2, NPCM_I2CADDR3, NPCM_I2CADDR4,
> > +     NPCM_I2CADDR5, NPCM_I2CADDR6, NPCM_I2CADDR7, NPCM_I2CADDR8,
> > +     NPCM_I2CADDR9, NPCM_I2CADDR10,
>
> Looks a bit hacky, but serves the purpose.
>
> The core issue in "npcm_i2c_slave_enable()" is the lack of an
> upper boundary check, which could potentially lead to a buffer
> overflow. In practice, we rely on the assumption that these
> addresses don’t exist in the real world.
>
> An easier fix could have been:
>
> @@ -629,7 +629,7 @@ static int npcm_i2c_slave_enable(struct npcm_i2c *bus, enum i2c_addr addr_type,
>         if (addr_type > I2C_SLAVE_ADDR2 && addr_type <= I2C_SLAVE_ADDR10)
>                 dev_err(bus->dev, "try to enable more than 2 SA not supported\n");
>
> -       if (addr_type >= I2C_ARP_ADDR)
> +       if (addr_type > I2C_SLAVE_ADDR2)
>                 return -EFAULT;
>
>         /* Set and enable the address */
>
> But yours is a bit more robust, so that I'm going to take this
> patch.
>
> Reviewed-by: Andi Shyti <andi.shyti@...nel.org>
>
> Thanks,
> Andi
>
> >  };
> >  #endif
> >
> > --
> > 2.34.1
> >

Thank you.

Regards,
Tyrone