drm/i915/userptr: Hold mmref whilst calling get-user-pages
Holding a reference to the containing task_struct is not sufficient to
prevent the mm_struct from being reaped under memory pressure. If this
happens whilst we are calling get_user_pages(), explosions erupt -
sometimes an immediate GPF, sometimes page flag corruption. To prevent
the target mm from being reaped as we are reading from it, acquire a
reference before we begin.
Testcase: igt/gem_shrink/*userptr
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: stable@vger.kernel.org
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1459864801-28606-2-git-send-email-chris@chris-wilson.co.uk
(cherry picked from commit 40313f0cd0
)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
This commit is contained in:
parent
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@ -501,9 +501,12 @@ __i915_gem_userptr_get_pages_worker(struct work_struct *_work)
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if (pvec != NULL) {
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struct mm_struct *mm = obj->userptr.mm->mm;
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ret = -EFAULT;
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if (atomic_inc_not_zero(&mm->mm_users)) {
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down_read(&mm->mmap_sem);
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while (pinned < npages) {
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ret = get_user_pages_remote(work->task, mm,
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ret = get_user_pages_remote
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(work->task, mm,
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obj->userptr.ptr + pinned * PAGE_SIZE,
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npages - pinned,
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!obj->userptr.read_only, 0,
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@ -514,6 +517,8 @@ __i915_gem_userptr_get_pages_worker(struct work_struct *_work)
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pinned += ret;
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}
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up_read(&mm->mmap_sem);
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mmput(mm);
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}
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}
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mutex_lock(&dev->struct_mutex);
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