linux-kernel - Re: [PATCH v2] i2c: xgene-slimpro: Fix out-of-bounds bug in xgene_slimpro_i2c

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Date:   Tue, 14 Mar 2023 23:43:41 +0800
From:   Wei Chen <harperchen1110@...il.com>
To:     Andi Shyti <andi.shyti@...nel.org>
Cc:     linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] i2c: xgene-slimpro: Fix out-of-bounds bug in xgene_slimpro_i2c_xfer()

The data->block[0] variable comes from user and is a number between
0-255. Without a proper check, the variable may be very large to cause
an out-of-bounds when performing memcpy in slimpro_i2c_blkwr.

Fix this bug by checking the value of writelen.

Signed-off-by: Wei Chen <harperchen1110@...il.com>
---
Changes in v2:
 - Put length check inside slimpro_i2c_blkwr

drivers/i2c/busses/i2c-xgene-slimpro.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/i2c/busses/i2c-xgene-slimpro.c
b/drivers/i2c/busses/i2c-xgene-slimpro.c
index bc9a3e7e0c96..0f7263e2276a 100644
--- a/drivers/i2c/busses/i2c-xgene-slimpro.c
+++ b/drivers/i2c/busses/i2c-xgene-slimpro.c
@@ -308,6 +308,9 @@ static int slimpro_i2c_blkwr(struct
slimpro_i2c_dev *ctx, u32 chip,
u32 msg[3];
int rc;
+ if (writelen > I2C_SMBUS_BLOCK_MAX)
+ return -EINVAL;
+
memcpy(ctx->dma_buffer, data, writelen);
paddr = dma_map_single(ctx->dev, ctx->dma_buffer, writelen,
DMA_TO_DEVICE);
-- 
2.25.1


On Tue, 14 Mar 2023 at 22:10, Andi Shyti <andi.shyti@...nel.org> wrote:
>
> Hi Wei,
>
> On Tue, Mar 14, 2023 at 01:57:34PM +0000, Wei Chen wrote:
> > The data->block[0] variable comes from user and is a number between
> > 0-255. Without proper check, the variable may be very large to cause
> > an out-of-bounds when performing memcpy in slimpro_i2c_blkwr.
> >
> > Fix this bug by checking the value of data->block[0].
> >
> > Signed-off-by: Wei Chen <harperchen1110@...il.com>
> > ---
> >  drivers/i2c/busses/i2c-xgene-slimpro.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> >
> > diff --git a/drivers/i2c/busses/i2c-xgene-slimpro.c b/drivers/i2c/busses/i2c-xgene-slimpro.c
> > index 63259b3ea5ab..bc9a3e7e0c96 100644
> > --- a/drivers/i2c/busses/i2c-xgene-slimpro.c
> > +++ b/drivers/i2c/busses/i2c-xgene-slimpro.c
> > @@ -391,6 +391,10 @@ static int xgene_slimpro_i2c_xfer(struct i2c_adapter *adap, u16 addr,
> >                                               &data->block[0]);
> >
> >               } else {
> > +
> > +                     if (data->block[0] + 1 > I2C_SMBUS_BLOCK_MAX)
> > +                             return -EINVAL;
> > +
> >                       ret = slimpro_i2c_blkwr(ctx, addr, command,
> >                                               SMBUS_CMD_LEN,
> >                                               SLIMPRO_IIC_SMB_PROTOCOL,
> > @@ -408,6 +412,10 @@ static int xgene_slimpro_i2c_xfer(struct i2c_adapter *adap, u16 addr,
> >                                               IIC_SMB_WITHOUT_DATA_LEN,
> >                                               &data->block[1]);
> >               } else {
> > +
> > +                     if (data->block[0] > I2C_SMBUS_BLOCK_MAX)
> > +                             return -EINVAL;
> > +
>
> you could eventually put this check inside slimpro_i2c_blkwr() so
> that you have it once and for all, for everyone.
>
> Andi
>
> >                       ret = slimpro_i2c_blkwr(ctx, addr, command,
> >                                               SMBUS_CMD_LEN,
> >                                               SLIMPRO_IIC_I2C_PROTOCOL,
> > --
> > 2.25.1
> >