[PATCH] drm/amdgpu: Fix snprintf usage in amdgpu_gfx_kiq_init_ring

[Srinivasan Shanmugam]

This commit fixes a format truncation issue arosed by the snprintf
function potentially writing more characters into the ring->name buffer
than it can hold, in the amdgpu_gfx_kiq_init_ring function

The issue occurred because the '%d' format specifier could write between
1 and 10 bytes into a region of size between 0 and 8, depending on the
  values of xcc_id, ring->me, ring->pipe, and ring->queue. The snprintf
function could output between 12 and 41 bytes into a destination of size
16, leading to potential truncation.

To resolve this, the snprintf line was modified to use the '%3d' and
'%1hhd' format specifiers. The '%3d' specifier is used for xcc_id and
ensures that it is always printed with a width of 3 characters. The
'%1hhd' specifier is used for ring->me, ring->pipe, and ring->queue, and
ensures that these values are printed as single digit numbers. This is
achieved by casting these values to unsigned char before passing them to
snprintf, which ensures that these values will always be in the range of
0 to 9.

Fixes the below with gcc W=1:
drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c: In function ‘amdgpu_gfx_kiq_init_ring’:
drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c:332:61: warning: ‘%d’ directive output may be truncated writing between 1 and 10 bytes into a region of size between 0 and 8 [-Wformat-truncation=]
  332 |         snprintf(ring->name, sizeof(ring->name), "kiq_%d.%d.%d.%d",
      |                                                             ^~
drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c:332:50: note: directive argument in the range [0, 2147483647]
  332 |         snprintf(ring->name, sizeof(ring->name), "kiq_%d.%d.%d.%d",
      |                                                  ^~~~~~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c:332:9: note: ‘snprintf’ output between 12 and 41 bytes into a destination of size 16
  332 |         snprintf(ring->name, sizeof(ring->name), "kiq_%d.%d.%d.%d",
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  333 |                  xcc_id, ring->me, ring->pipe, ring->queue);
      |                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fixes: 345a36c4f1ba ("drm/amdgpu: prefer snprintf over sprintf")
Cc: Alex Deucher <alexander.deucher at amd.com>
Cc: Christian König <christian.koenig at amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c
index 9b7dc61c331d..88da17c0340b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c
@@ -329,8 +329,9 @@ int amdgpu_gfx_kiq_init_ring(struct amdgpu_device *adev, int xcc_id)
 
 	ring->eop_gpu_addr = kiq->eop_gpu_addr;
 	ring->no_scheduler = true;
-	snprintf(ring->name, sizeof(ring->name), "kiq_%d.%d.%d.%d",
-		 xcc_id, ring->me, ring->pipe, ring->queue);
+	snprintf(ring->name, sizeof(ring->name), "kiq_%3d.%1hhd.%1hhd.%1hhd",
+		 xcc_id, (unsigned char)ring->me, (unsigned char)ring->pipe,
+		 (unsigned char)ring->queue);
 	r = amdgpu_ring_init(adev, ring, 1024, irq, AMDGPU_CP_KIQ_IRQ_DRIVER0,
 			     AMDGPU_RING_PRIO_DEFAULT, NULL);
 	if (r)
-- 
2.34.1