drm/amdgpu/vcn4: Prevent OOB reads when parsing IB

commit 2444eb0 upstream.

Rewrite the IB parsing to use amdgpu_ib_get_value() which handles the
bounds checks.

Signed-off-by: Benjamin Cheng <benjamin.cheng@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Ruijing Dong <ruijing.dong@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: lolzballs

drivers/gpu/drm/amd/amdgpu/vcn_v4_0.c

@@ -1755,9 +1755,10 @@ static int vcn_v4_0_dec_msg(struct amdgpu_cs_parser *p, struct amdgpu_job *job,
 static int vcn_v4_0_enc_find_ib_param(struct amdgpu_ib *ib, uint32_t id, int start)
 {
 	int i;
+	uint32_t len;
 
-	for (i = start; i < ib->length_dw && ib->ptr[i] >= 8; i += ib->ptr[i] / 4) {
-		if (ib->ptr[i + 1] == id)
+	for (i = start; (len = amdgpu_ib_get_value(ib, i)) >= 8; i += len / 4) {
+		if (amdgpu_ib_get_value(ib, i + 1) == id)
 			return i;
 	}
 	return -1;
@@ -1768,8 +1769,6 @@ static int vcn_v4_0_ring_patch_cs_in_place(struct amdgpu_cs_parser *p,
 					   struct amdgpu_ib *ib)
 {
 	struct amdgpu_ring *ring = amdgpu_job_ring(job);
-	struct amdgpu_vcn_decode_buffer *decode_buffer;
-	uint64_t addr;
 	uint32_t val;
 	int idx = 0, sidx;
 
@@ -1780,20 +1779,22 @@ static int vcn_v4_0_ring_patch_cs_in_place(struct amdgpu_cs_parser *p,
 	while ((idx = vcn_v4_0_enc_find_ib_param(ib, RADEON_VCN_ENGINE_INFO, idx)) >= 0) {
 		val = amdgpu_ib_get_value(ib, idx + 2); /* RADEON_VCN_ENGINE_TYPE */
 		if (val == RADEON_VCN_ENGINE_TYPE_DECODE) {
-			decode_buffer = (struct amdgpu_vcn_decode_buffer *)&ib->ptr[idx + 6];
+			uint32_t valid_buf_flag = amdgpu_ib_get_value(ib, idx + 6);
+			uint64_t msg_buffer_addr;
 
-			if (!(decode_buffer->valid_buf_flag & 0x1))
+			if (!(valid_buf_flag & 0x1))
 				return 0;
 
-			addr = ((u64)decode_buffer->msg_buffer_address_hi) << 32 |
-				decode_buffer->msg_buffer_address_lo;
-			return vcn_v4_0_dec_msg(p, job, addr);
+			msg_buffer_addr = ((u64)amdgpu_ib_get_value(ib, idx + 7)) << 32 |
+				amdgpu_ib_get_value(ib, idx + 8);
+			return vcn_v4_0_dec_msg(p, job, msg_buffer_addr);
 		} else if (val == RADEON_VCN_ENGINE_TYPE_ENCODE) {
 			sidx = vcn_v4_0_enc_find_ib_param(ib, RENCODE_IB_PARAM_SESSION_INIT, idx);
-			if (sidx >= 0 && ib->ptr[sidx + 2] == RENCODE_ENCODE_STANDARD_AV1)
+			if (sidx >= 0 &&
+			    amdgpu_ib_get_value(ib, sidx + 2) == RENCODE_ENCODE_STANDARD_AV1)
 				return vcn_v4_0_limit_sched(p, job);
 		}
-		idx += ib->ptr[idx] / 4;
+		idx += amdgpu_ib_get_value(ib, idx) / 4;
 	}
 	return 0;
 }