On 11/11/2019 15:42, Daniel Vetter wrote:
> On Mon, Nov 11, 2019 at 2:11 PM Steven Price <steven.price@xxxxxxx> wrote:
>>
>> On 04/11/2019 17:37, Daniel Vetter wrote:
>>> Full audit of everyone:
>>>
>>> - i915, radeon, amdgpu should be clean per their maintainers.
>>>
>>> - vram helpers should be fine, they don't do command submission, so
>>> really no business holding struct_mutex while doing copy_*_user. But
>>> I haven't checked them all.
>>>
>>> - panfrost seems to dma_resv_lock only in panfrost_job_push, which
>>> looks clean.
>>>
>>> - v3d holds dma_resv locks in the tail of its v3d_submit_cl_ioctl(),
>>> copying from/to userspace happens all in v3d_lookup_bos which is
>>> outside of the critical section.
>>>
>>> - vmwgfx has a bunch of ioctls that do their own copy_*_user:
>>> - vmw_execbuf_process: First this does some copies in
>>> vmw_execbuf_cmdbuf() and also in the vmw_execbuf_process() itself.
>>> Then comes the usual ttm reserve/validate sequence, then actual
>>> submission/fencing, then unreserving, and finally some more
>>> copy_to_user in vmw_execbuf_copy_fence_user. Glossing over tons of
>>> details, but looks all safe.
>>> - vmw_fence_event_ioctl: No ttm_reserve/dma_resv_lock anywhere to be
>>> seen, seems to only create a fence and copy it out.
>>> - a pile of smaller ioctl in vmwgfx_ioctl.c, no reservations to be
>>> found there.
>>> Summary: vmwgfx seems to be fine too.
>>>
>>> - virtio: There's virtio_gpu_execbuffer_ioctl, which does all the
>>> copying from userspace before even looking up objects through their
>>> handles, so safe. Plus the getparam/getcaps ioctl, also both safe.
>>>
>>> - qxl only has qxl_execbuffer_ioctl, which calls into
>>> qxl_process_single_command. There's a lovely comment before the
>>> __copy_from_user_inatomic that the slowpath should be copied from
>>> i915, but I guess that never happened. Try not to be unlucky and get
>>> your CS data evicted between when it's written and the kernel tries
>>> to read it. The only other copy_from_user is for relocs, but those
>>> are done before qxl_release_reserve_list(), which seems to be the
>>> only thing reserving buffers (in the ttm/dma_resv sense) in that
>>> code. So looks safe.
>>>
>>> - A debugfs file in nouveau_debugfs_pstate_set() and the usif ioctl in
>>> usif_ioctl() look safe. nouveau_gem_ioctl_pushbuf() otoh breaks this
>>> everywhere and needs to be fixed up.
>>>
>>> v2: Thomas pointed at that vmwgfx calls dma_resv_init while it holds a
>>> dma_resv lock of a different object already. Christian mentioned that
>>> ttm core does this too for ghost objects. intel-gfx-ci highlighted
>>> that i915 has similar issues.
>>>
>>> Unfortunately we can't do this in the usual module init functions,
>>> because kernel threads don't have an ->mm - we have to wait around for
>>> some user thread to do this.
>>>
>>> Solution is to spawn a worker (but only once). It's horrible, but it
>>> works.
>>>
>>> v3: We can allocate mm! (Chris). Horrible worker hack out, clean
>>> initcall solution in.
>>>
>>> v4: Annotate with __init (Rob Herring)
>>>
>>> Cc: Rob Herring <robh@xxxxxxxxxx>
>>> Cc: Alex Deucher <alexander.deucher@xxxxxxx>
>>> Cc: Christian König <christian.koenig@xxxxxxx>
>>> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
>>> Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
>>> Cc: Rob Herring <robh@xxxxxxxxxx>
>>> Cc: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>
>>> Cc: Eric Anholt <eric@xxxxxxxxxx>
>>> Cc: Dave Airlie <airlied@xxxxxxxxxx>
>>> Cc: Gerd Hoffmann <kraxel@xxxxxxxxxx>
>>> Cc: Ben Skeggs <bskeggs@xxxxxxxxxx>
>>> Cc: "VMware Graphics" <linux-graphics-maintainer@xxxxxxxxxx>
>>> Cc: Thomas Hellstrom <thellstrom@xxxxxxxxxx>
>>> Reviewed-by: Christian König <christian.koenig@xxxxxxx>
>>> Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
>>> Tested-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
>>> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
>>> ---
>>> drivers/dma-buf/dma-resv.c | 24 ++++++++++++++++++++++++
>>> 1 file changed, 24 insertions(+)
>>>
>>> diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
>>> index 709002515550..a05ff542be22 100644
>>> --- a/drivers/dma-buf/dma-resv.c
>>> +++ b/drivers/dma-buf/dma-resv.c
>>> @@ -34,6 +34,7 @@
>>>
>>> #include <linux/dma-resv.h>
>>> #include <linux/export.h>
>>> +#include <linux/sched/mm.h>
>>>
>>> /**
>>> * DOC: Reservation Object Overview
>>> @@ -95,6 +96,29 @@ static void dma_resv_list_free(struct dma_resv_list *list)
>>> kfree_rcu(list, rcu);
>>> }
>>>
>>> +#if IS_ENABLED(CONFIG_LOCKDEP)
>>> +static void __init dma_resv_lockdep(void)
>>> +{
>>> + struct mm_struct *mm = mm_alloc();
>>> + struct dma_resv obj;
>>> +
>>> + if (!mm)
>>> + return;
>>> +
>>> + dma_resv_init(&obj);
>>> +
>>> + down_read(&mm->mmap_sem);
>>> + ww_mutex_lock(&obj.lock, NULL);
>>> + fs_reclaim_acquire(GFP_KERNEL);
>>> + fs_reclaim_release(GFP_KERNEL);
>>> + ww_mutex_unlock(&obj.lock);
>>> + up_read(&mm->mmap_sem);
>>> +
>>
>> Nit: trailing whitespace
>>
>>> + mmput(mm);
>>> +}
>>> +subsys_initcall(dma_resv_lockdep);
>>
>> This expects a function returning int, but dma_resv_lockdep() is void.
>> Causing:
>>
>> drivers/dma-buf/dma-resv.c:119:17: error: initialization of ‘initcall_t’
>> {aka ‘int (*)(void)’} from incompatible pointer type ‘void (*)(void)’
>> [-Werror=incompatible-pointer-types]
>> subsys_initcall(dma_resv_lockdep);
>>
>> The below fixes it for me.
>
> Uh, so _that_ was what the 0day thing was all about, I totally misread
> that completely. Thanks for the patch.
>
> Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
>
> Aside, do you need commit rights for pushing this kind of stuff?
I guess it's about time I got round to requesting that:
https://gitlab.freedesktop.org/freedesktop/freedesktop/issues/208
Thanks,
Steve
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