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

[Mikhail Kobuk]

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 at ispras.ru>
---
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@ispras.ru/

 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
-- 
2.44.0