* [bug report] drm: xlnx: DRM/KMS driver for Xilinx ZynqMP DisplayPort Subsystem
@ 2020-07-27 11:18 dan.carpenter
2020-07-29 18:21 ` Hyun Kwon
0 siblings, 1 reply; 2+ messages in thread
From: dan.carpenter @ 2020-07-27 11:18 UTC (permalink / raw)
To: hyun.kwon; +Cc: dri-devel
Hello Hyun Kwon,
The patch d76271d22694: "drm: xlnx: DRM/KMS driver for Xilinx ZynqMP
DisplayPort Subsystem" from Jul 7, 2018, leads to the following
static checker warning:
drivers/gpu/drm/xlnx/zynqmp_dp.c:594 zynqmp_dp_mode_configure()
error: iterator underflow 'bws' (-1)-2
drivers/gpu/drm/xlnx/zynqmp_dp.c
566 static int zynqmp_dp_mode_configure(struct zynqmp_dp *dp, int pclock,
567 u8 current_bw)
568 {
569 int max_rate = dp->link_config.max_rate;
570 u8 bws[3] = { DP_LINK_BW_1_62, DP_LINK_BW_2_7, DP_LINK_BW_5_4 };
571 u8 max_lanes = dp->link_config.max_lanes;
572 u8 max_link_rate_code = drm_dp_link_rate_to_bw_code(max_rate);
573 u8 bpp = dp->config.bpp;
574 u8 lane_cnt;
575 s8 i;
576
577 if (current_bw == DP_LINK_BW_1_62) {
578 dev_err(dp->dev, "can't downshift. already lowest link rate\n");
579 return -EINVAL;
580 }
581
582 for (i = ARRAY_SIZE(bws) - 1; i >= 0; i--) {
^^^^^^
This exits with i == -1.
583 if (current_bw && bws[i] >= current_bw)
584 continue;
585
586 if (bws[i] <= max_link_rate_code)
587 break;
588 }
589
590 for (lane_cnt = 1; lane_cnt <= max_lanes; lane_cnt <<= 1) {
591 int bw;
592 u32 rate;
593
594 bw = drm_dp_bw_code_to_link_rate(bws[i]);
^^^^^^
Potential negative array offset.
595 rate = zynqmp_dp_max_rate(bw, lane_cnt, bpp);
596 if (pclock <= rate) {
597 dp->mode.bw_code = bws[i];
598 dp->mode.lane_cnt = lane_cnt;
599 dp->mode.pclock = pclock;
600 return dp->mode.bw_code;
601 }
602 }
603
604 dev_err(dp->dev, "failed to configure link values\n");
605
606 return -EINVAL;
607 }
regards,
dan carpenter
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^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [bug report] drm: xlnx: DRM/KMS driver for Xilinx ZynqMP DisplayPort Subsystem
2020-07-27 11:18 [bug report] drm: xlnx: DRM/KMS driver for Xilinx ZynqMP DisplayPort Subsystem dan.carpenter
@ 2020-07-29 18:21 ` Hyun Kwon
0 siblings, 0 replies; 2+ messages in thread
From: Hyun Kwon @ 2020-07-29 18:21 UTC (permalink / raw)
To: dan.carpenter; +Cc: dri-devel
Hi Dan,
Thanks for sharing.
On Mon, Jul 27, 2020 at 04:18:25AM -0700, dan.carpenter@oracle.com wrote:
> Hello Hyun Kwon,
>
> The patch d76271d22694: "drm: xlnx: DRM/KMS driver for Xilinx ZynqMP
> DisplayPort Subsystem" from Jul 7, 2018, leads to the following
> static checker warning:
>
> drivers/gpu/drm/xlnx/zynqmp_dp.c:594 zynqmp_dp_mode_configure()
> error: iterator underflow 'bws' (-1)-2
>
> drivers/gpu/drm/xlnx/zynqmp_dp.c
> 566 static int zynqmp_dp_mode_configure(struct zynqmp_dp *dp, int pclock,
> 567 u8 current_bw)
> 568 {
> 569 int max_rate = dp->link_config.max_rate;
> 570 u8 bws[3] = { DP_LINK_BW_1_62, DP_LINK_BW_2_7, DP_LINK_BW_5_4 };
> 571 u8 max_lanes = dp->link_config.max_lanes;
> 572 u8 max_link_rate_code = drm_dp_link_rate_to_bw_code(max_rate);
> 573 u8 bpp = dp->config.bpp;
> 574 u8 lane_cnt;
> 575 s8 i;
> 576
> 577 if (current_bw == DP_LINK_BW_1_62) {
> 578 dev_err(dp->dev, "can't downshift. already lowest link rate\n");
> 579 return -EINVAL;
> 580 }
There are checks like this that ensure the 'i' to be not negative, but I agree
it should be made clearer. I've sumitted a fix for it [1].
[1] https://lists.freedesktop.org/archives/dri-devel/2020-July/274190.html
Thanks,
-hyun
> 581
> 582 for (i = ARRAY_SIZE(bws) - 1; i >= 0; i--) {
> ^^^^^^
> This exits with i == -1.
>
> 583 if (current_bw && bws[i] >= current_bw)
> 584 continue;
> 585
> 586 if (bws[i] <= max_link_rate_code)
> 587 break;
> 588 }
> 589
> 590 for (lane_cnt = 1; lane_cnt <= max_lanes; lane_cnt <<= 1) {
> 591 int bw;
> 592 u32 rate;
> 593
> 594 bw = drm_dp_bw_code_to_link_rate(bws[i]);
> ^^^^^^
> Potential negative array offset.
>
> 595 rate = zynqmp_dp_max_rate(bw, lane_cnt, bpp);
> 596 if (pclock <= rate) {
> 597 dp->mode.bw_code = bws[i];
> 598 dp->mode.lane_cnt = lane_cnt;
> 599 dp->mode.pclock = pclock;
> 600 return dp->mode.bw_code;
> 601 }
> 602 }
> 603
> 604 dev_err(dp->dev, "failed to configure link values\n");
> 605
> 606 return -EINVAL;
> 607 }
>
> regards,
> dan carpenter
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel
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2020-07-27 11:18 [bug report] drm: xlnx: DRM/KMS driver for Xilinx ZynqMP DisplayPort Subsystem dan.carpenter
2020-07-29 18:21 ` Hyun Kwon
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