i2c: mux: demux-pinctrl: Annotate struct i2c_demux_pinctrl_priv with __counted_by

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct i2c_demux_pinctrl_priv.
Additionally, since the element count member must be set before accessing
the annotated flexible array member, move its initialization earlier.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
[wsa: improved blank lines]
Signed-off-by: Wolfram Sang <wsa@kernel.org>

diff --git a/drivers/i2c/muxes/i2c-demux-pinctrl.c b/drivers/i2c/muxes/i2c-demux-pinctrl.c
index a3a122fae71e09853200069e668b326e139eb90f..ee5fb60651e7977dcc15821ff53994fcf4cb0368 100644 (file)
--- a/drivers/i2c/muxes/i2c-demux-pinctrl.c
+++ b/drivers/i2c/muxes/i2c-demux-pinctrl.c
@@ -32,7 +32,7 @@ struct i2c_demux_pinctrl_priv {
        const char *bus_name;
        struct i2c_adapter cur_adap;
        struct i2c_algorithm algo;
-       struct i2c_demux_pinctrl_chan chan[];
+       struct i2c_demux_pinctrl_chan chan[] __counted_by(num_chan);
 };
 
 static int i2c_demux_master_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
@@ -226,6 +226,8 @@ static int i2c_demux_pinctrl_probe(struct platform_device *pdev)
        if (!priv || !props)
                return -ENOMEM;
 
+       priv->num_chan = num_chan;
+
        err = of_property_read_string(np, "i2c-bus-name", &priv->bus_name);
        if (err)
                return err;
@@ -249,9 +251,7 @@ static int i2c_demux_pinctrl_probe(struct platform_device *pdev)
                of_changeset_update_property(&priv->chan[i].chgset, adap_np, &props[i]);
        }
 
-       priv->num_chan = num_chan;
        priv->dev = &pdev->dev;
-
        platform_set_drvdata(pdev, priv);
 
        pm_runtime_no_callbacks(&pdev->dev);