[PATCH] drm/ttm: stop passing NULL fence in ttm_bo_move_sync_cleanup - dri-devel - freedesktop.org experimental mailing list

11 Apr 2022

If we hit the sync case, like when skipping clearing for kernel internal
objects, or when falling back to cpu clearing, like in i915, we end up
trying to add a NULL fence, but with some recent changes in this area
this now just results in NULL deref in dma_resv_add_fence:
<1>[    5.466383] BUG: kernel NULL pointer dereference, address: 0000000000000008
<1>[    5.466384] #PF: supervisor read access in kernel mode
<1>[    5.466385] #PF: error_code(0x0000) - not-present page
<6>[    5.466386] PGD 0 P4D 0
<4>[    5.466387] Oops: 0000 [#1] PREEMPT SMP NOPTI
<4>[    5.466389] CPU: 5 PID: 267 Comm: modprobe Not tainted 5.18.0-rc2-CI-CI_DRM_11481+ #1
<4>[    5.466391] RIP: 0010:dma_resv_add_fence+0x63/0x260
<4>[    5.466395] Code: 38 85 c0 0f 84 df 01 00 00 0f 88 e8 01 00 00 83 c0 01 0f 88 df 01 00 00 8b 05 35 89 10 01 49 8d 5e 68 85 c0 0f 85 45 01 00 00 <48> 8b 45 08 48 3d c0 a5 0a 82 0f 84 5c 01 00 00 48 3d 60 a5 0a 82
<4>[    5.466396] RSP: 0018:ffffc90000e974f8 EFLAGS: 00010202
<4>[    5.466397] RAX: 0000000000000001 RBX: ffff888123e88b28 RCX: 00000000ffffffff
<4>[    5.466398] RDX: 0000000000000001 RSI: ffffffff822e4f50 RDI: ffffffff8233f087
<4>[    5.466399] RBP: 0000000000000000 R08: ffff8881313dbc80 R09: 0000000000000001
<4>[    5.466399] R10: 0000000000000001 R11: 00000000da354294 R12: 0000000000000000
<4>[    5.466400] R13: ffff88810927dc58 R14: ffff888123e88ac0 R15: ffff88810a88d600
<4>[    5.466401] FS:  00007f5fa1193540(0000) GS:ffff88845d880000(0000) knlGS:0000000000000000
<4>[    5.466402] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
<4>[    5.466402] CR2: 0000000000000008 CR3: 0000000106dd6003 CR4: 00000000003706e0
<4>[    5.466403] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
<4>[    5.466404] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
<4>[    5.466404] Call Trace:
<4>[    5.466405]  <TASK>
<4>[    5.466406]  ttm_bo_move_accel_cleanup+0x62/0x270 [ttm]
<4>[    5.466411]  ? i915_rsgt_from_buddy_resource+0x185/0x1e0 [i915]
<4>[    5.466529]  i915_ttm_move+0xfd/0x430 [i915]
<4>[    5.466833]  ? dma_resv_reserve_fences+0x4e/0x320
<4>[    5.466836]  ? ttm_bo_add_move_fence.constprop.20+0xf7/0x140 [ttm]
<4>[    5.466841]  ttm_bo_handle_move_mem+0xa1/0x140 [ttm]
<4>[    5.466845]  ttm_bo_validate+0xee/0x160 [ttm]
<4>[    5.466849]  __i915_ttm_get_pages+0x4f/0x210 [i915]
<4>[    5.466976]  i915_ttm_get_pages+0xad/0x140 [i915]
<4>[    5.467094]  ____i915_gem_object_get_pages+0x32/0xf0 [i915]
<4>[    5.467210]  __i915_gem_object_get_pages+0x89/0xa0 [i915]
<4>[    5.467323]  i915_vma_get_pages+0x114/0x1d0 [i915]
<4>[    5.467446]  i915_vma_pin_ww+0xd3/0xa90 [i915]
<4>[    5.467570]  i915_vma_pin.constprop.10+0x119/0x1b0 [i915]
<4>[    5.467700]  ? __mutex_unlock_slowpath+0x3e/0x2b0
<4>[    5.467704]  intel_alloc_initial_plane_obj.isra.6+0x1a9/0x390 [i915]
<4>[    5.467833]  intel_crtc_initial_plane_config+0x83/0x340 [i915]
In the ttm_bo_move_sync_cleanup() case it seems we only really care
about calling ttm_bo_wait_free_node(), so let's instead just call that
directly.
Signed-off-by: Matthew Auld matthew.auld@intel.com
Cc: Thomas Hellström thomas.hellstrom@linux.intel.com
Cc: Christian König christian.koenig@amd.com
Cc: Lucas De Marchi lucas.demarchi@intel.com
Cc: Nirmoy Das nirmoy.das@linux.intel.com
---
 drivers/gpu/drm/ttm/ttm_bo_util.c | 15 +++++++++++++++
 include/drm/ttm/ttm_bo_driver.h   | 11 +++--------
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
index bc5190340b9c..1cbfb00c1d65 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_util.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
@@ -572,6 +572,21 @@ int ttm_bo_move_accel_cleanup(struct ttm_buffer_object *bo,
 }
 EXPORT_SYMBOL(ttm_bo_move_accel_cleanup);
+void ttm_bo_move_sync_cleanup(struct ttm_buffer_object *bo,
+			      struct ttm_resource *new_mem)
+{
+	struct ttm_device *bdev = bo->bdev;
+	struct ttm_resource_manager *man = ttm_manager_type(bdev, new_mem->mem_type);
+	int ret;
+
+	ret = ttm_bo_wait_free_node(bo, man->use_tt);
+	if (WARN_ON(ret))
+		return;
+
+	ttm_bo_assign_mem(bo, new_mem);
+}
+EXPORT_SYMBOL(ttm_bo_move_sync_cleanup);
+
 /**
  * ttm_bo_pipeline_gutting - purge the contents of a bo
  * @bo: The buffer object
diff --git a/include/drm/ttm/ttm_bo_driver.h b/include/drm/ttm/ttm_bo_driver.h
index 059a595e14e5..897b88f0bd59 100644
--- a/include/drm/ttm/ttm_bo_driver.h
+++ b/include/drm/ttm/ttm_bo_driver.h
@@ -245,7 +245,7 @@ int ttm_bo_move_accel_cleanup(struct ttm_buffer_object *bo,
    		      struct ttm_resource *new_mem);
/**
- * ttm_bo_move_accel_cleanup.
+ * ttm_bo_move_sync_cleanup.
  *
  * @bo: A pointer to a struct ttm_buffer_object.
  * @new_mem: struct ttm_resource indicating where to move.
@@ -253,13 +253,8 @@ int ttm_bo_move_accel_cleanup(struct ttm_buffer_object *bo,
  * Special case of ttm_bo_move_accel_cleanup where the bo is guaranteed
  * by the caller to be idle. Typically used after memcpy buffer moves.
  */
-static inline void ttm_bo_move_sync_cleanup(struct ttm_buffer_object *bo,
-					    struct ttm_resource *new_mem)
-{
-	int ret = ttm_bo_move_accel_cleanup(bo, NULL, true, false, new_mem);
-
-	WARN_ON(ret);
-}
+void ttm_bo_move_sync_cleanup(struct ttm_buffer_object *bo,
+			      struct ttm_resource *new_mem);
/**
  * ttm_bo_pipeline_gutting.
-- 
2.34.1


    