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

BugLink: https://bugs.launchpad.net/bugs/2059991

[ Upstream commit 58fca35 ]

'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 on the
stream_enc_regs array.

Thus fixing Buffer overflow error in dcn301_stream_encoder_create
reported by Smatch:
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: 3a83e4e ("drm/amd/display: Add dcn3.01 support to DC (v2)")
Cc: Roman Li <[email protected]>
Cc: Rodrigo Siqueira <[email protected]>
Cc: Aurabindo Pillai <[email protected]>
Signed-off-by: Srinivasan Shanmugam <[email protected]>
Reviewed-by: Roman Li <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
Signed-off-by: Portia Stephens <[email protected]>
Signed-off-by: Roxana Nicolescu <[email protected]>

Author: srishanm

drivers/gpu/drm/amd/display/dc/dcn301/dcn301_resource.c

@@ -996,7 +996,7 @@ static struct stream_encoder *dcn301_stream_encoder_create(enum engine_id eng_id
 	vpg = dcn301_vpg_create(ctx, vpg_inst);
 	afmt = dcn301_afmt_create(ctx, afmt_inst);
 
-	if (!enc1 || !vpg || !afmt) {
+	if (!enc1 || !vpg || !afmt || eng_id >= ARRAY_SIZE(stream_enc_regs)) {
 		kfree(enc1);
 		kfree(vpg);
 		kfree(afmt);