Commit 40313f0c authored by Chris Wilson's avatar Chris Wilson

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: default avatarChris 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: default avatarMichał Winiarski <michal.winiarski@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1459864801-28606-2-git-send-email-chris@chris-wilson.co.uk
parent 393afc2c
......@@ -544,19 +544,24 @@ __i915_gem_userptr_get_pages_worker(struct work_struct *_work)
if (pvec != NULL) {
struct mm_struct *mm = obj->userptr.mm->mm;
down_read(&mm->mmap_sem);
while (pinned < npages) {
ret = get_user_pages_remote(work->task, mm,
obj->userptr.ptr + pinned * PAGE_SIZE,
npages - pinned,
!obj->userptr.read_only, 0,
pvec + pinned, NULL);
if (ret < 0)
break;
pinned += ret;
ret = -EFAULT;
if (atomic_inc_not_zero(&mm->mm_users)) {
down_read(&mm->mmap_sem);
while (pinned < npages) {
ret = get_user_pages_remote
(work->task, mm,
obj->userptr.ptr + pinned * PAGE_SIZE,
npages - pinned,
!obj->userptr.read_only, 0,
pvec + pinned, NULL);
if (ret < 0)
break;
pinned += ret;
}
up_read(&mm->mmap_sem);
mmput(mm);
}
up_read(&mm->mmap_sem);
}
mutex_lock(&dev->struct_mutex);
......
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