[PATCH] lib: sbi_dbtr: fix shared memory double-fetch in install_trig

[liutong]

sbi_dbtr_install_trig() reads trigger configuration from S-mode shared
memory in two separate loops: first to validate, then to install. Since
the shared memory remains writable by S-mode between the two reads, the
data used for installation may differ from what was validated.

Fix this by taking a snapshot of the shared memory into a local buffer
and performing both validation and installation against that snapshot.
Also add a bounds check on trig_count against RV_MAX_TRIGGERS to prevent
out-of-bounds access on the local buffer.

Additionally, fix a redundant read in dbtr_trigger_setup() where tdata1
was read from the message pointer a second time instead of using the
value already saved in trig->tdata1, which could lead to inconsistency
between the CSR write and the trigger state setup.

Signed-off-by: liutong <liutong at iscas.ac.cn>
---
 lib/sbi/sbi_dbtr.c | 52 +++++++++++++++++++++++++---------------------
 1 file changed, 28 insertions(+), 24 deletions(-)

diff --git a/lib/sbi/sbi_dbtr.c b/lib/sbi/sbi_dbtr.c
index 01047969..8bad2d95 100644
--- a/lib/sbi/sbi_dbtr.c
+++ b/lib/sbi/sbi_dbtr.c
@@ -327,7 +327,7 @@ static void dbtr_trigger_setup(struct sbi_dbtr_trigger *trig,
 	trig->tdata2 = lle_to_cpu(recv->tdata2);
 	trig->tdata3 = lle_to_cpu(recv->tdata3);
 
-	tdata1 = lle_to_cpu(recv->tdata1);
+	tdata1 = trig->tdata1;
 
 	trig->state = 0;
 
@@ -603,14 +603,15 @@ int sbi_dbtr_read_trig(unsigned long smode,
 int sbi_dbtr_install_trig(unsigned long smode,
 			  unsigned long trig_count, unsigned long *out)
 {
+	struct sbi_dbtr_data_msg local_data[RV_MAX_TRIGGERS];
 	void *shmem_base = NULL;
 	union sbi_dbtr_shmem_entry *entry;
-	struct sbi_dbtr_data_msg *recv;
 	struct sbi_dbtr_id_msg *xmit;
 	unsigned long ctrl;
 	struct sbi_dbtr_trigger *trig;
 	struct sbi_dbtr_hart_triggers_state *hs = NULL;
 	bool tdata2_impl, tdata3_impl;
+	int i;
 
 	hs = dbtr_thishart_state_ptr();
 	if (!hs)
@@ -619,9 +620,22 @@ int sbi_dbtr_install_trig(unsigned long smode,
 	if (sbi_dbtr_shmem_disabled(hs))
 		return SBI_ERR_NO_SHMEM;
 
+	if (trig_count > RV_MAX_TRIGGERS)
+		return SBI_ERR_INVALID_PARAM;
+
 	shmem_base = hart_shmem_base(hs);
+
+	/*
+	 * Snapshot trigger data from shared memory into a local buffer so
+	 * that S-mode cannot modify the data between validation and use.
+	 */
 	sbi_hart_protection_map_range((unsigned long)shmem_base,
 				      trig_count * sizeof(*entry));
+	for_each_trig_entry(shmem_base, trig_count, typeof(*entry), entry) {
+		local_data[_idx] = entry->data;
+	}
+	sbi_hart_protection_unmap_range((unsigned long)shmem_base,
+					trig_count * sizeof(*entry));
 
 	/*
 	 * SBI v3.0 sec 19.4 requires SBI_ERR_NOT_SUPPORTED when a trigger
@@ -632,42 +646,35 @@ int sbi_dbtr_install_trig(unsigned long smode,
 	tdata2_impl = tdata_implemented(CSR_TDATA2);
 	tdata3_impl = tdata_implemented(CSR_TDATA3);
 
-	/* Check requested triggers configuration */
-	for_each_trig_entry(shmem_base, trig_count, typeof(*entry), entry) {
-		recv = (struct sbi_dbtr_data_msg *)(&entry->data);
-		ctrl = recv->tdata1;
+	/* Validate triggers from the local snapshot */
+	for (i = 0; i < (int)trig_count; i++) {
+		ctrl = local_data[i].tdata1;
 
 		if (!dbtr_trigger_supported(TDATA1_GET_TYPE(ctrl))) {
-			*out = _idx;
-			sbi_hart_protection_unmap_range((unsigned long)shmem_base,
-							trig_count * sizeof(*entry));
+			*out = i;
 			return SBI_ERR_FAILED;
 		}
 
 		if (!dbtr_trigger_valid(TDATA1_GET_TYPE(ctrl), ctrl)) {
-			*out = _idx;
-			sbi_hart_protection_unmap_range((unsigned long)shmem_base,
-							trig_count * sizeof(*entry));
+			*out = i;
 			return SBI_ERR_FAILED;
 		}
 
-		if ((recv->tdata2 && !tdata2_impl) ||
-		    (recv->tdata3 && !tdata3_impl)) {
-			*out = _idx;
-			sbi_hart_protection_unmap_range((unsigned long)shmem_base,
-							trig_count * sizeof(*entry));
+		if ((local_data[i].tdata2 && !tdata2_impl) ||
+		    (local_data[i].tdata3 && !tdata3_impl)) {
+			*out = i;
 			return SBI_ERR_NOT_SUPPORTED;
 		}
 	}
 
 	if (hs->available_trigs < trig_count) {
 		*out = hs->available_trigs;
-		sbi_hart_protection_unmap_range((unsigned long)shmem_base,
-					       trig_count * sizeof(*entry));
 		return SBI_ERR_FAILED;
 	}
 
-	/* Install triggers */
+	/* Install triggers from the validated local snapshot */
+	sbi_hart_protection_map_range((unsigned long)shmem_base,
+				      trig_count * sizeof(*entry));
 	for_each_trig_entry(shmem_base, trig_count, typeof(*entry), entry) {
 		/*
 		 * Since we have already checked if enough triggers are
@@ -675,15 +682,12 @@ int sbi_dbtr_install_trig(unsigned long smode,
 		 */
 		trig = sbi_alloc_trigger();
 
-		recv = (struct sbi_dbtr_data_msg *)(&entry->data);
 		xmit = (struct sbi_dbtr_id_msg *)(&entry->id);
 
-		dbtr_trigger_setup(trig,  recv);
+		dbtr_trigger_setup(trig, &local_data[_idx]);
 		dbtr_trigger_enable(trig);
 		xmit->idx = cpu_to_lle(trig->index);
-
 	}
-
 	sbi_hart_protection_unmap_range((unsigned long)shmem_base,
 					trig_count * sizeof(*entry));
 
-- 
2.34.1