Re: [PATCH v4] ptp: ocp: Limit signal/freq counts in show/store functions

[Vadim Fedorenko <vadim.fedorenko@linux.dev>]

On 11.05.2025 16:42, Sagi Maimon wrote:
> The sysfs show/store operations could access uninitialized elements
> in the freq_in[] and signal_out[] arrays, leading to NULL pointer
> dereferences. This patch introduces u8 fields (nr_freq_in,
> nr_signal_out) to track the number of initialized elements, capping
> the maximum at 4 for each array. The show/store functions are updated
> to respect these limits, preventing out-of-bounds access and ensuring
> safe array handling.
> 
> Signed-off-by: Sagi Maimon <maimon.sagi@gmail.com>
> ---
> Addressed comments from Vadim Fedorenko:
>   - https://www.spinics.net/lists/netdev/msg1090730.html
> Changes since v3:
>   - in signal/freq show routine put constant string "UNSUPPORTED" in
>     output instead of returning error.
> ---
> ---
>   drivers/ptp/ptp_ocp.c | 40 +++++++++++++++++++++++++++++++++-------
>   1 file changed, 33 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/ptp/ptp_ocp.c b/drivers/ptp/ptp_ocp.c
> index 2ccdca4f6960..14b4b3bebccd 100644
> --- a/drivers/ptp/ptp_ocp.c
> +++ b/drivers/ptp/ptp_ocp.c
> @@ -315,6 +315,8 @@ struct ptp_ocp_serial_port {
>   #define OCP_BOARD_ID_LEN		13
>   #define OCP_SERIAL_LEN			6
>   #define OCP_SMA_NUM			4
> +#define OCP_SIGNAL_NUM			4
> +#define OCP_FREQ_NUM			4
>   
>   enum {
>   	PORT_GNSS,
> @@ -342,8 +344,8 @@ struct ptp_ocp {
>   	struct dcf_master_reg	__iomem *dcf_out;
>   	struct dcf_slave_reg	__iomem *dcf_in;
>   	struct tod_reg		__iomem *nmea_out;
> -	struct frequency_reg	__iomem *freq_in[4];
> -	struct ptp_ocp_ext_src	*signal_out[4];
> +	struct frequency_reg	__iomem *freq_in[OCP_FREQ_NUM];
> +	struct ptp_ocp_ext_src	*signal_out[OCP_SIGNAL_NUM];
>   	struct ptp_ocp_ext_src	*pps;
>   	struct ptp_ocp_ext_src	*ts0;
>   	struct ptp_ocp_ext_src	*ts1;
> @@ -378,10 +380,12 @@ struct ptp_ocp {
>   	u32			utc_tai_offset;
>   	u32			ts_window_adjust;
>   	u64			fw_cap;
> -	struct ptp_ocp_signal	signal[4];
> +	struct ptp_ocp_signal	signal[OCP_SIGNAL_NUM];
>   	struct ptp_ocp_sma_connector sma[OCP_SMA_NUM];
>   	const struct ocp_sma_op *sma_op;
>   	struct dpll_device *dpll;
> +	int signals_nr;
> +	int freq_in_nr;
>   };
>   
>   #define OCP_REQ_TIMESTAMP	BIT(0)
> @@ -2697,6 +2701,8 @@ ptp_ocp_fb_board_init(struct ptp_ocp *bp, struct ocp_resource *r)
>   	bp->eeprom_map = fb_eeprom_map;
>   	bp->fw_version = ioread32(&bp->image->version);
>   	bp->sma_op = &ocp_fb_sma_op;
> +	bp->signals_nr = 4;
> +	bp->freq_in_nr = 4;
>   
>   	ptp_ocp_fb_set_version(bp);
>   
> @@ -2862,6 +2868,8 @@ ptp_ocp_art_board_init(struct ptp_ocp *bp, struct ocp_resource *r)
>   	bp->fw_version = ioread32(&bp->reg->version);
>   	bp->fw_tag = 2;
>   	bp->sma_op = &ocp_art_sma_op;
> +	bp->signals_nr = 4;
> +	bp->freq_in_nr = 4;
>   
>   	/* Enable MAC serial port during initialisation */
>   	iowrite32(1, &bp->board_config->mro50_serial_activate);
> @@ -2888,6 +2896,8 @@ ptp_ocp_adva_board_init(struct ptp_ocp *bp, struct ocp_resource *r)
>   	bp->flash_start = 0xA00000;
>   	bp->eeprom_map = fb_eeprom_map;
>   	bp->sma_op = &ocp_adva_sma_op;
> +	bp->signals_nr = 2;
> +	bp->freq_in_nr = 2;
>   
>   	version = ioread32(&bp->image->version);
>   	/* if lower 16 bits are empty, this is the fw loader. */
> @@ -3190,6 +3200,9 @@ signal_store(struct device *dev, struct device_attribute *attr,
>   	if (!argv)
>   		return -ENOMEM;
>   
> +	if (gen >= bp->signals_nr)
> +		return -EINVAL;
> +
>   	err = -EINVAL;
>   	s.duty = bp->signal[gen].duty;
>   	s.phase = bp->signal[gen].phase;
> @@ -3247,6 +3260,10 @@ signal_show(struct device *dev, struct device_attribute *attr, char *buf)
>   	int i;
>   
>   	i = (uintptr_t)ea->var;
> +
> +	if (i >= bp->signals_nr)
> +		return sysfs_emit(buf, "UNSUPPORTED\n");
> +
>   	signal = &bp->signal[i];

I've checked the code again. Jakub is right, there is no need to modify
singal/seconds/frequency show/set functions. Now I'm not quite sure how is it
possible to reach this functions with unsupported input? You export a specific
set of attributes for your card:

static const struct ocp_attr_group adva_timecard_groups[] = {
	{ .cap = OCP_CAP_BASIC,	    .group = &adva_timecard_group },
	{ .cap = OCP_CAP_BASIC,	    .group = &ptp_ocp_timecard_tty_group },
	{ .cap = OCP_CAP_SIGNAL,    .group = &fb_timecard_signal0_group },
	{ .cap = OCP_CAP_SIGNAL,    .group = &fb_timecard_signal1_group },
	{ .cap = OCP_CAP_FREQ,	    .group = &fb_timecard_freq0_group },
	{ .cap = OCP_CAP_FREQ,	    .group = &fb_timecard_freq1_group },
	{ },
};

It has only freq1, freq2, gen1, gen2 attributes exported to sysfs. How can it
happen that you can change freq3 or gen3?

The only problem I see is in the summary output - that should be addressed with
this patch (well, you've done it already).

>   
>   	count = sysfs_emit(buf, "%llu %d %llu %d", signal->period,
> @@ -3359,6 +3376,9 @@ seconds_store(struct device *dev, struct device_attribute *attr,
>   	u32 val;
>   	int err;
>   
> +	if (idx >= bp->freq_in_nr)
> +		return -EINVAL;
> +
>   	err = kstrtou32(buf, 0, &val);
>   	if (err)
>   		return err;
> @@ -3381,6 +3401,9 @@ seconds_show(struct device *dev, struct device_attribute *attr, char *buf)
>   	int idx = (uintptr_t)ea->var;
>   	u32 val;
>   
> +	if (idx >= bp->freq_in_nr)
> +		return sysfs_emit(buf, "UNSUPPORTED\n");
> +
>   	val = ioread32(&bp->freq_in[idx]->ctrl);
>   	if (val & 1)
>   		val = (val >> 8) & 0xff;
> @@ -3402,6 +3425,9 @@ frequency_show(struct device *dev, struct device_attribute *attr, char *buf)
>   	int idx = (uintptr_t)ea->var;
>   	u32 val;
>   
> +	if (idx >= bp->freq_in_nr)
> +		return -EINVAL;
> +
>   	val = ioread32(&bp->freq_in[idx]->status);
>   	if (val & FREQ_STATUS_ERROR)
>   		return sysfs_emit(buf, "error\n");
> @@ -4008,7 +4034,7 @@ _signal_summary_show(struct seq_file *s, struct ptp_ocp *bp, int nr)
>   {
>   	struct signal_reg __iomem *reg = bp->signal_out[nr]->mem;
>   	struct ptp_ocp_signal *signal = &bp->signal[nr];
> -	char label[8];
> +	char label[16];
>   	bool on;
>   	u32 val;
>   
> @@ -4031,7 +4057,7 @@ static void
>   _frequency_summary_show(struct seq_file *s, int nr,
>   			struct frequency_reg __iomem *reg)
>   {
> -	char label[8];
> +	char label[16];
>   	bool on;
>   	u32 val;
>   
> @@ -4175,11 +4201,11 @@ ptp_ocp_summary_show(struct seq_file *s, void *data)
>   	}
>   
>   	if (bp->fw_cap & OCP_CAP_SIGNAL)
> -		for (i = 0; i < 4; i++)
> +		for (i = 0; i < bp->signals_nr; i++)
>   			_signal_summary_show(s, bp, i);
>   
>   	if (bp->fw_cap & OCP_CAP_FREQ)
> -		for (i = 0; i < 4; i++)
> +		for (i = 0; i < bp->freq_in_nr; i++)
>   			_frequency_summary_show(s, i, bp->freq_in[i]);
>   
>   	if (bp->irig_out) {

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