[PATCH 8/8] firmware: arm_ffa: Bound PARTITION_INFO_GET_REGS copies

[Sudeep Holla <sudeep.holla@kernel.org>]

The register-based PARTITION_INFO_GET path trusted the firmware-provided
indices when copying partition descriptors into the caller buffer.
Reject inconsistent counts or index progressions so the copy loop cannot
write past the allocated array.

Fixes: ba85c644ac8d ("firmware: arm_ffa: Add support for FFA_PARTITION_INFO_GET_REGS")
Signed-off-by: Sudeep Holla <sudeep.holla@kernel.org>
---
 drivers/firmware/arm_ffa/driver.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/arm_ffa/driver.c b/drivers/firmware/arm_ffa/driver.c
index 40ade6edcf33..4bb86eb721cd 100644
--- a/drivers/firmware/arm_ffa/driver.c
+++ b/drivers/firmware/arm_ffa/driver.c
@@ -336,7 +336,7 @@ __ffa_partition_info_get_regs(u32 uuid0, u32 uuid1, u32 uuid2, u32 uuid3,
 
 	do {
 		__le64 *regs;
-		int idx;
+		int idx, nr_desc, buf_idx;
 
 		start_idx = prev_idx ? prev_idx + 1 : 0;
 
@@ -354,15 +354,25 @@ __ffa_partition_info_get_regs(u32 uuid0, u32 uuid1, u32 uuid2, u32 uuid3,
 			count = PARTITION_COUNT(partition_info.a2);
 		if (!buffer || !num_parts) /* count only */
 			return count;
+		if (count > num_parts)
+			return -EINVAL;
 
 		cur_idx = CURRENT_INDEX(partition_info.a2);
+		if (cur_idx < start_idx || cur_idx >= count)
+			return -EINVAL;
+
+		nr_desc = cur_idx - start_idx + 1;
+		buf_idx = buf - buffer;
+		if (buf_idx + nr_desc > num_parts)
+			return -EINVAL;
+
 		tag = UUID_INFO_TAG(partition_info.a2);
 		buf_sz = PARTITION_INFO_SZ(partition_info.a2);
 		if (buf_sz > sizeof(*buffer))
 			buf_sz = sizeof(*buffer);
 
 		regs = (void *)&partition_info.a3;
-		for (idx = 0; idx < cur_idx - start_idx + 1; idx++, buf++) {
+		for (idx = 0; idx < nr_desc; idx++, buf++) {
 			union {
 				uuid_t uuid;
 				u64 regs[2];

-- 
2.43.0