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abde491143
eng_id can be negative and that stream_enc_regs[]
can be indexed out of bounds.
eng_id is used directly as an index into stream_enc_regs[], which has
only 5 entries. When eng_id is 5 (ENGINE_ID_DIGF) or negative, this can
access memory past the end of the array.
Add a bounds check using ARRAY_SIZE() before using eng_id as an index.
The unsigned cast also rejects negative values.
This avoids out-of-bounds access.
Fixes the below smatch error:
dcn*_resource.c: stream_encoder_create() may index
stream_enc_regs[eng_id] out of bounds (size 5).
drivers/gpu/drm/amd/amdgpu/../display/dc/resource/dcn351/dcn351_resource.c
1246 static struct stream_encoder *dcn35_stream_encoder_create(
1247 enum engine_id eng_id,
1248 struct dc_context *ctx)
1249 {
...
1255
1256 /* Mapping of VPG, AFMT, DME register blocks to DIO block instance */
1257 if (eng_id <= ENGINE_ID_DIGF) {
ENGINE_ID_DIGF is 5. should <= be <?
Unrelated but, ugh, why is Smatch saying that "eng_id" can be negative?
end_id is type signed long, but there are checks in the caller which prevent it from being negative.
1258 vpg_inst = eng_id;
1259 afmt_inst = eng_id;
1260 } else
1261 return NULL;
1262
...
1281
1282 dcn35_dio_stream_encoder_construct(enc1, ctx, ctx->dc_bios,
1283 eng_id, vpg, afmt,
--> 1284 &stream_enc_regs[eng_id],
^^^^^^^^^^^^^^^^^^^^^^^ This stream_enc_regs[] array has 5 elements so we are one element beyond the end of the array.
...
1287 return &enc1->base;
1288 }
v2: use explicit bounds check as suggested by Roman/Dan; avoid unsigned int cast
v3: The compiler already knows how to compare the two values, so the
cast (int) is not needed. (Roman)
Fixes: 2728e9c7c8 ("drm/amd/display: add DC changes for DCN351")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Mario Limonciello <superm1@kernel.org>
Cc: Alex Hung <alex.hung@amd.com>
Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Cc: ChiaHsuan Chung <chiahsuan.chung@amd.com>
Cc: Roman Li <roman.li@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Roman Li <roman.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
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