4.2.8-ckt9 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------ From: Chris Wilson <ch...@chris-wilson.co.uk> commit db9f9203e27495b2d151b695504e286eec026e9b upstream. 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 <ch...@chris-wilson.co.uk> Cc: Tvrtko Ursulin <tvrtko.ursu...@intel.com> Cc: Michał Winiarski <michal.winiar...@intel.com> Reviewed-by: Michał Winiarski <michal.winiar...@intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/1459864801-28606-2-git-send-email-ch...@chris-wilson.co.uk (cherry picked from commit 40313f0cd0b711a7a5905e5182422799e157d8aa) Signed-off-by: Jani Nikula <jani.nik...@intel.com> [ kamal: backport to 4.2-stable: s/get_user_pages_remote/get_user_pages/ ] Signed-off-by: Kamal Mostafa <ka...@canonical.com> --- drivers/gpu/drm/i915/i915_gem_userptr.c | 29 +++++++++++++++++------------ 1 file changed, 17 insertions(+), 12 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c index 4037f89..76d8290 100644 --- a/drivers/gpu/drm/i915/i915_gem_userptr.c +++ b/drivers/gpu/drm/i915/i915_gem_userptr.c @@ -610,19 +610,24 @@ __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(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 + (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); -- 2.7.4
