[PATCH v2 2/4] lib: sbi: Add the bound check for events during config match

[Atish Patra]

Currently, there is no sanity check for firmware event code. We don't see
any issue as Linux kernel driver does a bound check on firmware events
already. However, OpenSBI can't assume sane supervisor mode software
always. Thus, an invalid event idx can cause a buffer overflow error.
For hardware events, the match will fail for invalid event code anyways.
However, a search is unecessary if event code is invalid.

Add a event ID validation function to solve the issue.

Signed-off-by: Atish Patra <atishp at rivosinc.com>
---
 lib/sbi/sbi_pmu.c | 39 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 37 insertions(+), 2 deletions(-)

diff --git a/lib/sbi/sbi_pmu.c b/lib/sbi/sbi_pmu.c
index 31631a2fab80..1170cba43b3d 100644
--- a/lib/sbi/sbi_pmu.c
+++ b/lib/sbi/sbi_pmu.c
@@ -107,6 +107,37 @@ static bool pmu_event_select_overlap(struct sbi_pmu_hw_event *evt,
 	return FALSE;
 }
 
+static int pmu_event_validate(unsigned long event_idx)
+{
+	uint32_t event_idx_type = get_cidx_type(event_idx);
+	uint32_t event_idx_code = get_cidx_code(event_idx);
+	uint32_t event_idx_code_max = -1;
+
+	switch(event_idx_type) {
+	case SBI_PMU_EVENT_TYPE_HW:
+		event_idx_code_max = SBI_PMU_HW_GENERAL_MAX;
+		break;
+	case SBI_PMU_EVENT_TYPE_FW:
+		event_idx_code_max = SBI_PMU_FW_MAX;
+		break;
+	case SBI_PMU_EVENT_TYPE_HW_CACHE:
+		event_idx_code_max = ((SBI_PMU_HW_CACHE_MAX & 0xFFF) << 0x03) |
+				       (SBI_PMU_HW_CACHE_OP_MAX & 0x3) << 0x01 |
+					0x01;
+		break;
+	case SBI_PMU_EVENT_TYPE_HW_RAW:
+		event_idx_code_max = 1; // event_idx.code should be zero
+		break;
+	default:
+		return SBI_EINVAL;
+	}
+
+	if (event_idx_code < event_idx_code_max)
+		return event_idx_type;
+	else
+		return SBI_EINVAL;
+}
+
 static int pmu_ctr_validate(uint32_t cidx, uint32_t *event_idx_code)
 {
 	uint32_t event_idx_val;
@@ -614,12 +645,16 @@ int sbi_pmu_ctr_cfg_match(unsigned long cidx_base, unsigned long cidx_mask,
 {
 	int ctr_idx = SBI_ENOTSUPP;
 	u32 hartid = current_hartid();
-	int event_type = get_cidx_type(event_idx);
+	int event_type;
 	struct sbi_pmu_fw_event *fevent;
 	uint32_t fw_evt_code;
 
 	/* Do a basic sanity check of counter base & mask */
-	if ((cidx_base + sbi_fls(cidx_mask)) >= total_ctrs || event_type >= SBI_PMU_EVENT_TYPE_MAX)
+	if ((cidx_base + sbi_fls(cidx_mask)) >= total_ctrs)
+		return SBI_EINVAL;
+
+	event_type = pmu_event_validate(event_idx);
+	if (event_type < 0)
 		return SBI_EINVAL;
 
 	if (flags & SBI_PMU_CFG_FLAG_SKIP_MATCH) {
-- 
2.25.1