Re: [PATCH v2] drm: nv04: Fix out of bounds access

[Danilo Krummrich]

On 4/11/24 13:08, Mikhail Kobuk wrote:
> When Output Resource (dcb->or) value is assigned in
> fabricate_dcb_output(), there may be out of bounds access to
> dac_users array in case dcb->or is zero because ffs(dcb->or) is
> used as index there.
> The 'or' argument of fabricate_dcb_output() must be interpreted as a
> number of bit to set, not value.
>
> Utilize macros from 'enum nouveau_or' in calls instead of hardcoding.
>
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>
> Fixes: 2e5702aff395 ("drm/nouveau: fabricate DCB encoder table for iMac G4")
> Fixes: 670820c0e6a9 ("drm/nouveau: Workaround incorrect DCB entry on a GeForce3 Ti 200.")
> Signed-off-by: Mikhail Kobuk <m.kobuk@xxxxxxxxx>

Applied to drm-misc-fixes, thanks!

> ---
> Changes in v2:
> - Instead of checking ffs(dcb->or), adjust function calls to match
>    argument semantics
> - Link to v1: https://lore.kernel.org/all/20240331064552.6112-1-m.kobuk@xxxxxxxxx/
>
>   drivers/gpu/drm/nouveau/nouveau_bios.c | 13 +++++++------
>   1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_bios.c b/drivers/gpu/drm/nouveau/nouveau_bios.c
> index 479effcf607e..79cfab53f80e 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_bios.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_bios.c
> @@ -23,6 +23,7 @@
>    */
>   
>   #include "nouveau_drv.h"
> +#include "nouveau_bios.h"
>   #include "nouveau_reg.h"
>   #include "dispnv04/hw.h"
>   #include "nouveau_encoder.h"
> @@ -1677,7 +1678,7 @@ apply_dcb_encoder_quirks(struct drm_device *dev, int idx, u32 *conn, u32 *conf)
>   	 */
>   	if (nv_match_device(dev, 0x0201, 0x1462, 0x8851)) {
>   		if (*conn == 0xf2005014 && *conf == 0xffffffff) {
> -			fabricate_dcb_output(dcb, DCB_OUTPUT_TMDS, 1, 1, 1);
> +			fabricate_dcb_output(dcb, DCB_OUTPUT_TMDS, 1, 1, DCB_OUTPUT_B);
>   			return false;
>   		}
>   	}
> @@ -1763,26 +1764,26 @@ fabricate_dcb_encoder_table(struct drm_device *dev, struct nvbios *bios)
>   #ifdef __powerpc__
>   	/* Apple iMac G4 NV17 */
>   	if (of_machine_is_compatible("PowerMac4,5")) {
> -		fabricate_dcb_output(dcb, DCB_OUTPUT_TMDS, 0, all_heads, 1);
> -		fabricate_dcb_output(dcb, DCB_OUTPUT_ANALOG, 1, all_heads, 2);
> +		fabricate_dcb_output(dcb, DCB_OUTPUT_TMDS, 0, all_heads, DCB_OUTPUT_B);
> +		fabricate_dcb_output(dcb, DCB_OUTPUT_ANALOG, 1, all_heads, DCB_OUTPUT_C);
>   		return;
>   	}
>   #endif
>   
>   	/* Make up some sane defaults */
>   	fabricate_dcb_output(dcb, DCB_OUTPUT_ANALOG,
> -			     bios->legacy.i2c_indices.crt, 1, 1);
> +			     bios->legacy.i2c_indices.crt, 1, DCB_OUTPUT_B);
>   
>   	if (nv04_tv_identify(dev, bios->legacy.i2c_indices.tv) >= 0)
>   		fabricate_dcb_output(dcb, DCB_OUTPUT_TV,
>   				     bios->legacy.i2c_indices.tv,
> -				     all_heads, 0);
> +				     all_heads, DCB_OUTPUT_A);
>   
>   	else if (bios->tmds.output0_script_ptr ||
>   		 bios->tmds.output1_script_ptr)
>   		fabricate_dcb_output(dcb, DCB_OUTPUT_TMDS,
>   				     bios->legacy.i2c_indices.panel,
> -				     all_heads, 1);
> +				     all_heads, DCB_OUTPUT_B);
>   }
>   
>   static int