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Subject[PATCH 5.4 105/191] drm/amdgpu: Call find_vma under mmap_sem
Date
From: Jason Gunthorpe <jgg@mellanox.com>

[ Upstream commit a9ae8731e6e52829a935d81a65d7f925cb95dbac ]

find_vma() must be called under the mmap_sem, reorganize this code to
do the vma check after entering the lock.

Further, fix the unlocked use of struct task_struct's mm, instead use
the mm from hmm_mirror which has an active mm_grab. Also the mm_grab
must be converted to a mm_get before acquiring mmap_sem or calling
find_vma().

Fixes: 66c45500bfdc ("drm/amdgpu: use new HMM APIs and helpers")
Fixes: 0919195f2b0d ("drm/amdgpu: Enable amdgpu_ttm_tt_get_user_pages in worker threads")
Link: https://lore.kernel.org/r/20191112202231.3856-11-jgg@ziepe.ca
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Philip Yang <Philip.Yang@amd.com>
Tested-by: Philip Yang <Philip.Yang@amd.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 37 ++++++++++++++-----------
1 file changed, 21 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index dff41d0a85fe..c0e41f1f0c23 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -35,6 +35,7 @@
#include <linux/hmm.h>
#include <linux/pagemap.h>
#include <linux/sched/task.h>
+#include <linux/sched/mm.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/swap.h>
@@ -788,7 +789,7 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
struct hmm_mirror *mirror = bo->mn ? &bo->mn->mirror : NULL;
struct ttm_tt *ttm = bo->tbo.ttm;
struct amdgpu_ttm_tt *gtt = (void *)ttm;
- struct mm_struct *mm = gtt->usertask->mm;
+ struct mm_struct *mm;
unsigned long start = gtt->userptr;
struct vm_area_struct *vma;
struct hmm_range *range;
@@ -796,25 +797,14 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
uint64_t *pfns;
int r = 0;

- if (!mm) /* Happens during process shutdown */
- return -ESRCH;
-
if (unlikely(!mirror)) {
DRM_DEBUG_DRIVER("Failed to get hmm_mirror\n");
- r = -EFAULT;
- goto out;
+ return -EFAULT;
}

- vma = find_vma(mm, start);
- if (unlikely(!vma || start < vma->vm_start)) {
- r = -EFAULT;
- goto out;
- }
- if (unlikely((gtt->userflags & AMDGPU_GEM_USERPTR_ANONONLY) &&
- vma->vm_file)) {
- r = -EPERM;
- goto out;
- }
+ mm = mirror->hmm->mmu_notifier.mm;
+ if (!mmget_not_zero(mm)) /* Happens during process shutdown */
+ return -ESRCH;

range = kzalloc(sizeof(*range), GFP_KERNEL);
if (unlikely(!range)) {
@@ -847,6 +837,17 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
hmm_range_wait_until_valid(range, HMM_RANGE_DEFAULT_TIMEOUT);

down_read(&mm->mmap_sem);
+ vma = find_vma(mm, start);
+ if (unlikely(!vma || start < vma->vm_start)) {
+ r = -EFAULT;
+ goto out_unlock;
+ }
+ if (unlikely((gtt->userflags & AMDGPU_GEM_USERPTR_ANONONLY) &&
+ vma->vm_file)) {
+ r = -EPERM;
+ goto out_unlock;
+ }
+
r = hmm_range_fault(range, 0);
up_read(&mm->mmap_sem);

@@ -865,15 +866,19 @@ int amdgpu_ttm_tt_get_user_pages(struct amdgpu_bo *bo, struct page **pages)
}

gtt->range = range;
+ mmput(mm);

return 0;

+out_unlock:
+ up_read(&mm->mmap_sem);
out_free_pfns:
hmm_range_unregister(range);
kvfree(pfns);
out_free_ranges:
kfree(range);
out:
+ mmput(mm);
return r;
}

--
2.20.1


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