[Intel-gfx] [PATCH v2] drm/i915: fix one mem leak in mmap_offset_attach()

[Chuansheng Liu]

The below memory leak information is caught:

unreferenced object 0xffff997dd4e3b240 (size 64):
  comm "gem_tiled_fence", pid 10332, jiffies 4294959326 (age
220778.420s)
  hex dump (first 32 bytes):
    01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 be f2 d4 7d 99 ff ff  ............}...
  backtrace:
    [<ffffffffa0f04365>] kmem_cache_alloc_trace+0x2e5/0x450
    [<ffffffffc062f3ac>] drm_vma_node_allow+0x2c/0xe0 [drm]
    [<ffffffffc13149ea>] __assign_mmap_offset_handle+0x1da/0x4a0 [i915]
    [<ffffffffc1315235>] i915_gem_mmap_offset_ioctl+0x55/0xb0 [i915]
    [<ffffffffc06207e4>] drm_ioctl_kernel+0xb4/0x140 [drm]
    [<ffffffffc0620ac7>] drm_ioctl+0x257/0x410 [drm]
    [<ffffffffa0f553ae>] __x64_sys_ioctl+0x8e/0xc0
    [<ffffffffa1821128>] do_syscall_64+0x38/0xc0
[<ffffffffa1a0007c>] entry_SYSCALL_64_after_hwframe+0x44/0xae

The issue is always reproduced with the test:
gem_tiled_fence_blits --run-subtest basic

It tries to mmap_gtt the same object several times, it is like:
create BO
mmap_gtt BO
unmap BO
mmap_gtt BO <== second time mmap_gtt
unmap
close BO

The leak happens at the second time mmap_gtt in function
mmap_offset_attach(),it will simply increase the reference
count to 2 by calling drm_vma_node_allow() directly since
the mmo has been created at the first time.

However the driver just revokes the vma_node only one time
when closing the object, it leads to memory leak easily.

This patch is to fix the memory leak by calling drm_vma_node_allow() one
time also.

V2: add "Fixes and Cc stable". (Tvrtko Ursulin)

Fixes: 786555987207 ("drm/i915/gem: Store mmap_offsets in an rbtree
rather than a plain list")
Cc: <stable at vger.kernel.org> # v5.7+
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Signed-off-by: Chuansheng Liu <chuansheng.liu at intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_mman.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
index c3ea243d414d..fda346d687fd 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
@@ -680,7 +680,7 @@ mmap_offset_attach(struct drm_i915_gem_object *obj,
 	mmo = insert_mmo(obj, mmo);
 	GEM_BUG_ON(lookup_mmo(obj, mmap_type) != mmo);
 out:
-	if (file)
+	if (file && !drm_vma_node_is_allowed(&mmo->vma_node, file))
 		drm_vma_node_allow(&mmo->vma_node, file);
 	return mmo;
 
-- 
2.25.0.rc2