Re: [PATCH] drm/amdgpu: Fix a potential sdma invalid access
From: Qu Huang
Date: Tue Apr 06 2021 - 02:07:43 EST
Hi Christian,
On 2021/4/3 16:49, Christian König wrote:
Hi Qu,
Am 03.04.21 um 07:08 schrieb Qu Huang:
Hi Christian,
On 2021/4/3 0:25, Christian König wrote:
Hi Qu,
Am 02.04.21 um 05:18 schrieb Qu Huang:
Before dma_resv_lock(bo->base.resv, NULL) in
amdgpu_bo_release_notify(),
the bo->base.resv lock may be held by ttm_mem_evict_first(),
That can't happen since when bo_release_notify is called the BO has not
more references and is therefore deleted.
And we never evict a deleted BO, we just wait for it to become idle.
Yes, the bo reference counter return to zero will enter
ttm_bo_release(),but notify bo release (call amdgpu_bo_release_notify())
first happen, and then test if a reservation object's fences have been
signaled, and then mark bo as deleted and remove bo from the LRU list.
When ttm_bo_release() and ttm_mem_evict_first() is concurrent,
the Bo has not been removed from the LRU list and is not marked as
deleted, this will happen.
Not sure on which code base you are, but I don't see how this can happen.
ttm_mem_evict_first() calls ttm_bo_get_unless_zero() and
ttm_bo_release() is only called when the BO reference count becomes zero.
So ttm_mem_evict_first() will see that this BO is about to be destroyed
and skips it.
Yes, you are right. My version of TTM is ROCM 3.3, so
ttm_mem_evict_first() did not call ttm_bo_get_unless_zero(), check that
ROCM 4.0 ttm doesn't have this issue. This is an oversight on my part.
As a test, when we use CPU memset instead of SDMA fill in
amdgpu_bo_release_notify(), the result is page fault:
PID: 5490 TASK: ffff8e8136e04100 CPU: 4 COMMAND: "gemmPerf"
#0 [ffff8e79eaa17970] machine_kexec at ffffffffb2863784
#1 [ffff8e79eaa179d0] __crash_kexec at ffffffffb291ce92
#2 [ffff8e79eaa17aa0] crash_kexec at ffffffffb291cf80
#3 [ffff8e79eaa17ab8] oops_end at ffffffffb2f6c768
#4 [ffff8e79eaa17ae0] no_context at ffffffffb2f5aaa6
#5 [ffff8e79eaa17b30] __bad_area_nosemaphore at ffffffffb2f5ab3d
#6 [ffff8e79eaa17b80] bad_area_nosemaphore at ffffffffb2f5acae
#7 [ffff8e79eaa17b90] __do_page_fault at ffffffffb2f6f6c0
#8 [ffff8e79eaa17c00] do_page_fault at ffffffffb2f6f925
#9 [ffff8e79eaa17c30] page_fault at ffffffffb2f6b758
[exception RIP: memset+31]
RIP: ffffffffb2b8668f RSP: ffff8e79eaa17ce8 RFLAGS: 00010a17
RAX: bebebebebebebebe RBX: ffff8e747bff10c0 RCX: 0000060b00200000
RDX: 0000000000000000 RSI: 00000000000000be RDI: ffffab807f000000
RBP: ffff8e79eaa17d10 R8: ffff8e79eaa14000 R9: ffffab7c80000000
R10: 000000000000bcba R11: 00000000000001ba R12: ffff8e79ebaa4050
R13: ffffab7c80000000 R14: 0000000000022600 R15: ffff8e8136e04100
ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
#10 [ffff8e79eaa17ce8] amdgpu_bo_release_notify at ffffffffc092f2d1
[amdgpu]
#11 [ffff8e79eaa17d18] ttm_bo_release at ffffffffc08f39dd [amdttm]
#12 [ffff8e79eaa17d58] amdttm_bo_put at ffffffffc08f3c8c [amdttm]
#13 [ffff8e79eaa17d68] amdttm_bo_vm_close at ffffffffc08f7ac9 [amdttm]
#14 [ffff8e79eaa17d80] remove_vma at ffffffffb29ef115
#15 [ffff8e79eaa17da0] exit_mmap at ffffffffb29f2c64
#16 [ffff8e79eaa17e58] mmput at ffffffffb28940c7
#17 [ffff8e79eaa17e78] do_exit at ffffffffb289dc95
#18 [ffff8e79eaa17f10] do_group_exit at ffffffffb289e4cf
#19 [ffff8e79eaa17f40] sys_exit_group at ffffffffb289e544
#20 [ffff8e79eaa17f50] system_call_fastpath at ffffffffb2f74ddb
Well that might be perfectly expected. VRAM is not necessarily CPU
accessible.
As a test，use CPU memset instead of SDMA fill, This is my code:
void amdgpu_bo_release_notify(struct ttm_buffer_object *bo)
{
struct amdgpu_bo *abo;
uint64_t num_pages;
struct drm_mm_node *mm_node;
struct amdgpu_device *adev;
void __iomem *kaddr;
if (!amdgpu_bo_is_amdgpu_bo(bo))
return;
abo = ttm_to_amdgpu_bo(bo);
num_pages = abo->tbo.num_pages;
mm_node = abo->tbo.mem.mm_node;
adev = amdgpu_ttm_adev(abo->tbo.bdev);
kaddr = adev->mman.aper_base_kaddr;
if (abo->kfd_bo)
amdgpu_amdkfd_unreserve_memory_limit(abo);
if (bo->mem.mem_type != TTM_PL_VRAM || !bo->mem.mm_node ||
!(abo->flags & AMDGPU_GEM_CREATE_VRAM_WIPE_ON_RELEASE))
return;
dma_resv_lock(amdkcl_ttm_resvp(bo), NULL);
while (num_pages && mm_node) {
void *ptr = kaddr + (mm_node->start << PAGE_SHIFT);
memset_io(ptr, AMDGPU_POISON & 0xff, mm_node->size <<PAGE_SHIFT);
num_pages -= mm_node->size;
++mm_node;
}
dma_resv_unlock(amdkcl_ttm_resvp(bo));
}
I have used the old version through oversight, so I am sorry for your
trouble.
Regards,
Qu.
Regards,
Christian.
Regards,
Qu.
Regards,
Christian.
and the VRAM mem will be evicted, mem region was replaced
by Gtt mem region. amdgpu_bo_release_notify() will then
hold the bo->base.resv lock, and SDMA will get an invalid
address in amdgpu_fill_buffer(), resulting in a VMFAULT
or memory corruption.
To avoid it, we have to hold bo->base.resv lock first, and
check whether the mem.mem_type is TTM_PL_VRAM.
Signed-off-by: Qu Huang <jinsdb@xxxxxxx>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
index 4b29b82..8018574 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
@@ -1300,12 +1300,16 @@ void amdgpu_bo_release_notify(struct
ttm_buffer_object *bo)
if (bo->base.resv == &bo->base._resv)
amdgpu_amdkfd_remove_fence_on_pt_pd_bos(abo);
- if (bo->mem.mem_type != TTM_PL_VRAM || !bo->mem.mm_node ||
- !(abo->flags & AMDGPU_GEM_CREATE_VRAM_WIPE_ON_RELEASE))
+ if (!(abo->flags & AMDGPU_GEM_CREATE_VRAM_WIPE_ON_RELEASE))
return;
dma_resv_lock(bo->base.resv, NULL);
+ if (bo->mem.mem_type != TTM_PL_VRAM || !bo->mem.mm_node) {
+ dma_resv_unlock(bo->base.resv);
+ return;
+ }
+
r = amdgpu_fill_buffer(abo, AMDGPU_POISON, bo->base.resv,
&fence);
if (!WARN_ON(r)) {
amdgpu_bo_fence(abo, fence, false);
--
1.8.3.1