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

[Sagi Maimon <maimon.sagi@gmail.com>]

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];
 
 	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) {
-- 
2.47.0