[PATCH] drm/amd/display: Implement bounds check for stream encoder creation in DCN301

[Srinivasan Shanmugam]

'stream_enc_regs' array is an array of dcn10_stream_enc_registers
structures. The array is initialized with four elements, corresponding
to the four calls to stream_enc_regs() in the array initializer. This
means that valid indices for this array are 0, 1, 2, and 3.

The error message 'stream_enc_regs' 4 <= 5 below, is indicating that
there is an attempt to access this array with an index of 5, which is
out of bounds. This could lead to undefined behavior

Here, eng_id is used as an index to access the stream_enc_regs array. If
eng_id is 5, this would result in an out-of-bounds access.

Fixes the below:
drivers/gpu/drm/amd/amdgpu/../display/dc/resource/dcn301/dcn301_resource.c:1011 dcn301_stream_encoder_create() error: buffer overflow 'stream_enc_regs' 4 <= 5

Fixes: 3a83e4e64bb1 ("drm/amd/display: Add dcn3.01 support to DC (v2)")
Cc: Roman Li <Roman.Li at amd.com>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira at amd.com>
Cc: Aurabindo Pillai <aurabindo.pillai at amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam at amd.com>
---
 .../display/dc/resource/dcn301/dcn301_resource.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/resource/dcn301/dcn301_resource.c b/drivers/gpu/drm/amd/display/dc/resource/dcn301/dcn301_resource.c
index 511ff6b5b985..f915d7c3980e 100644
--- a/drivers/gpu/drm/amd/display/dc/resource/dcn301/dcn301_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/resource/dcn301/dcn301_resource.c
@@ -1006,10 +1006,18 @@ static struct stream_encoder *dcn301_stream_encoder_create(enum engine_id eng_id
 		return NULL;
 	}
 
-	dcn30_dio_stream_encoder_construct(enc1, ctx, ctx->dc_bios,
-					eng_id, vpg, afmt,
-					&stream_enc_regs[eng_id],
-					&se_shift, &se_mask);
+	if (eng_id < ARRAY_SIZE(stream_enc_regs)) {
+		dcn30_dio_stream_encoder_construct(enc1, ctx, ctx->dc_bios,
+						   eng_id, vpg, afmt,
+						   &stream_enc_regs[eng_id],
+						   &se_shift, &se_mask);
+	} else {
+		DRM_ERROR("Invalid engine id: %d\n", eng_id);
+		kfree(enc1);
+		kfree(vpg);
+		kfree(afmt);
+		return NULL;
+	}
 
 	return &enc1->base;
 }
-- 
2.34.1