[PATCH 6.6 207/299] drm/amd/display: Fix buffer overflow in get_host_router_total_dp_tunnel_bw()

Greg Kroah-Hartman
2024-02-27T13:56:19Z

From: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>

commit 97cba232549b9fe7e491fb60a69cf93075015f29 upstream.

The error message buffer overflow 'dc->links' 12 <= 12 suggests that the
code is trying to access an element of the dc->links array that is
beyond its bounds. In C, arrays are zero-indexed, so an array with 12
elements has valid indices from 0 to 11. Trying to access dc->links[12]
would be an attempt to access the 13th element of a 12-element array,
which is a buffer overflow.

To fix this, ensure that the loop does not go beyond the last valid
index when accessing dc->links[i + 1] by subtracting 1 from the loop
condition.

This would ensure that i + 1 is always a valid index in the array.

Fixes the below:
drivers/gpu/drm/amd/amdgpu/../display/dc/link/protocols/link_dp_dpia_bw.c:208 get_host_router_total_dp_tunnel_bw() error: buffer overflow 'dc->links' 12 <= 12

Fixes: 59f1622a5f05 ("drm/amd/display: Add dpia display mode validation logic")
Cc: PeiChen Huang <peichen.huang@amd.com>
Cc: Aric Cyr <aric.cyr@amd.com>
Cc: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Cc: Meenakshikumar Somasundaram <meenakshikumar.somasundaram@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_dpia_bw.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_dpia_bw.c
+++ b/drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_dpia_bw.c
@@ -196,7 +196,7 @@ static int get_host_router_total_dp_tunn
struct dc_link *link_dpia_primary, *link_dpia_secondary;
int total_bw = 0;

- for (uint8_t i = 0; i < MAX_PIPES * 2; ++i) {
+ for (uint8_t i = 0; i < (MAX_PIPES * 2) - 1; ++i) {

if (!dc->links[i] || dc->links[i]->ep_type != DISPLAY_ENDPOINT_USB4_DPIA)
continue;