Messages in this thread Patch in this message | | | Subject | Re: [PATCH] drm/amdgpu: Fix a potential sdma invalid access | From | Qu Huang <> | Date | Sat, 3 Apr 2021 13:08:44 +0800 |
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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.
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
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@126.com> >> --- >> 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 >>
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