Messages in this thread | | | Date | Tue, 9 Aug 2022 09:28:36 +0800 | Subject | Re: [PATCH v2] drm/gem: Fix GEM handle release errors | From | Chen Jeffy <> |
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Hi Christian,
On 8/9 星期二 2:03, Christian König wrote: > Hi Jeffy, > > Am 08.08.22 um 05:51 schrieb Chen Jeffy: >> Hi Christian, >> >> Thanks for your reply, and sorry i didn't make it clear. >> >> On 8/8 星期一 0:52, Christian König wrote: >>> Am 03.08.22 um 10:32 schrieb Jeffy Chen: >>>> Currently we are assuming a one to one mapping between dmabuf and >>>> handle >>>> when releasing GEM handles. >>>> >>>> But that is not always true, since we would create extra handles for >>>> the >>>> GEM obj in cases like gem_open() and getfb{,2}(). >>>> >>>> A similar issue was reported at: >>>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fall%2F20211105083308.392156-1-jay.xu%40rock-chips.com%2F&data=05%7C01%7Cchristian.koenig%40amd.com%7Cd7488e9f235041f7e84408da78f14882%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637955274964656400%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=9G2YbHcYUs1VQYyvjXwLzYawNw%2BP8i%2BjjPBSHx3r2yg%3D&reserved=0 >>>> >>>> Another problem is that the drm_gem_remove_prime_handles() now only >>>> remove handle to the exported dmabuf (gem_obj->dma_buf), so the >>>> imported >>>> ones would leak: >>>> WARNING: CPU: 2 PID: 236 at drivers/gpu/drm/drm_prime.c:228 >>>> drm_prime_destroy_file_private+0x18/0x24 >>>> >>>> Let's fix these by using handle to find the exact map to remove. >>> >>> Well we are clearly something missing here. As far as I can see the >>> current code is correct. >>> >>> Creating multiple GEM handles for the same DMA-buf is possible, but >>> illegal. > >>> In other words when a GEM handle is exported as DMA-buf and imported >>> again you should intentionally always get the same handle. >> >> These issue are not about having handles for importing an exported >> dma-buf case, but for having multiple handles to a GEM object(which >> means having multiple handles to a dma-buf). >> >> I know the drm-prime is trying to make dma-buf and handle maps one to >> one, but the drm-gem is allowing to create extra handles for a GEM >> object, for example: >> drm_gem_open_ioctl -> drm_gem_handle_create_tail >> drm_mode_getfb2_ioctl -> drm_gem_handle_create >> drm_mode_getfb -> fb->funcs->create_handle > > Yes, so far that's correct. > >> >> >> So we are allowing GEM object to have multiple handles, and GEM object >> could have at most one dma-buf, doesn't that means that dma-buf could >> map to multiple handles? > > No, at least not for the same GEM file private. That's the reason why > the rb is indexed by the dma_buf object and not the handle. > > In other words the rb is so that you have exactly one handle for each > dma_buf in each file private.
I don't think so, because if user get multiple handles for the same GEM obj and use drm_gem_prime_handle_to_fd() for those handles, the current code would try to add multiple maps to rb: drm_prime_add_buf_handle(buf_1, hdl_1) drm_prime_add_buf_handle(buf_1, hdl_2) ... drm_prime_add_buf_handle(buf_1, hdl_n)
> >> >> Or should we rewrite the GEM framework to limit GEM object with uniq >> handle? > > No, the extra handles are expected because when you call > drm_mode_getfb*() and drm_gem_open_ioctl() the caller now owns the > returned GEM handle. > >> >> The other issue is that we are leaking dma-buf <-> handle map for the >> imported dma-buf, since the drm_gem_remove_prime_handles doesn't take >> care of obj->import_attach->dmabuf. > > No, that's correct as well. obj->dma_buf is set even for imported > DMA-buf objects. See drm_gem_prime_fd_to_handle().
Well, that obj->dma_buf would be set in drm_gem_prime_fd_to_handle(create new handle), and cleared when releasing the latest handle(release handle).
So it doesn't cover other handle creating path.
For example, a imported dma buf: drm_gem_prime_fd_to_handle <-- we got a handle and obj->dma_buf and obj->import_attach->dmabuf drm_gem_handle_delete <-- we lost that handle and obj->dma_buf cleared drm_gem_open_ioctl/or getfb* <-- we got a new handle and obj->import_attach->dmabuf drm_gem_handle_delete <-- we lost that handle and obj->dma_buf is null, which means rb leaks.
> > Regards, > Christian. > >> >> But of cause this can be fixed in other way: >> +++ b/drivers/gpu/drm/drm_gem.c >> @@ -180,6 +180,9 @@ drm_gem_remove_prime_handles(struct drm_gem_object >> *obj, struct drm_file *filp) >> drm_prime_remove_buf_handle_locked(&filp->prime, >> obj->dma_buf); >> } >> + if (obj->import_attach) >> + drm_prime_remove_buf_handle_locked(&filp->prime, >> + obj->import_attach->dmabuf); >> mutex_unlock(&filp->prime.lock); >> } >> >> >>> So this is pretty much a clear NAK to this patch since it shouldn't >>> be necessary or something is seriously broken somewhere else. >>> >>> Regards, >>> Christian. >>> >>>> >>>> Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com> >>>> --- >>>> >>>> Changes in v2: >>>> Fix a typo of rbtree. >>>> >>>> drivers/gpu/drm/drm_gem.c | 17 +---------------- >>>> drivers/gpu/drm/drm_internal.h | 4 ++-- >>>> drivers/gpu/drm/drm_prime.c | 20 ++++++++++++-------- >>>> 3 files changed, 15 insertions(+), 26 deletions(-) >>>> >>>> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c >>>> index eb0c2d041f13..ed39da383570 100644 >>>> --- a/drivers/gpu/drm/drm_gem.c >>>> +++ b/drivers/gpu/drm/drm_gem.c >>>> @@ -168,21 +168,6 @@ void drm_gem_private_object_init(struct >>>> drm_device *dev, >>>> } >>>> EXPORT_SYMBOL(drm_gem_private_object_init); >>>> -static void >>>> -drm_gem_remove_prime_handles(struct drm_gem_object *obj, struct >>>> drm_file *filp) >>>> -{ >>>> - /* >>>> - * Note: obj->dma_buf can't disappear as long as we still hold a >>>> - * handle reference in obj->handle_count. >>>> - */ >>>> - mutex_lock(&filp->prime.lock); >>>> - if (obj->dma_buf) { >>>> - drm_prime_remove_buf_handle_locked(&filp->prime, >>>> - obj->dma_buf); >>>> - } >>>> - mutex_unlock(&filp->prime.lock); >>>> -} >>>> - >>>> /** >>>> * drm_gem_object_handle_free - release resources bound to >>>> userspace handles >>>> * @obj: GEM object to clean up. >>>> @@ -253,7 +238,7 @@ drm_gem_object_release_handle(int id, void *ptr, >>>> void *data) >>>> if (obj->funcs->close) >>>> obj->funcs->close(obj, file_priv); >>>> - drm_gem_remove_prime_handles(obj, file_priv); >>>> + drm_prime_remove_buf_handle(&file_priv->prime, id); >>>> drm_vma_node_revoke(&obj->vma_node, file_priv); >>>> drm_gem_object_handle_put_unlocked(obj); >>>> diff --git a/drivers/gpu/drm/drm_internal.h >>>> b/drivers/gpu/drm/drm_internal.h >>>> index 1fbbc19f1ac0..7bb98e6a446d 100644 >>>> --- a/drivers/gpu/drm/drm_internal.h >>>> +++ b/drivers/gpu/drm/drm_internal.h >>>> @@ -74,8 +74,8 @@ int drm_prime_fd_to_handle_ioctl(struct drm_device >>>> *dev, void *data, >>>> void drm_prime_init_file_private(struct drm_prime_file_private >>>> *prime_fpriv); >>>> void drm_prime_destroy_file_private(struct drm_prime_file_private >>>> *prime_fpriv); >>>> -void drm_prime_remove_buf_handle_locked(struct >>>> drm_prime_file_private *prime_fpriv, >>>> - struct dma_buf *dma_buf); >>>> +void drm_prime_remove_buf_handle(struct drm_prime_file_private >>>> *prime_fpriv, >>>> + uint32_t handle); >>>> /* drm_drv.c */ >>>> struct drm_minor *drm_minor_acquire(unsigned int minor_id); >>>> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c >>>> index e3f09f18110c..bd5366b16381 100644 >>>> --- a/drivers/gpu/drm/drm_prime.c >>>> +++ b/drivers/gpu/drm/drm_prime.c >>>> @@ -190,29 +190,33 @@ static int drm_prime_lookup_buf_handle(struct >>>> drm_prime_file_private *prime_fpri >>>> return -ENOENT; >>>> } >>>> -void drm_prime_remove_buf_handle_locked(struct >>>> drm_prime_file_private *prime_fpriv, >>>> - struct dma_buf *dma_buf) >>>> +void drm_prime_remove_buf_handle(struct drm_prime_file_private >>>> *prime_fpriv, >>>> + uint32_t handle) >>>> { >>>> struct rb_node *rb; >>>> - rb = prime_fpriv->dmabufs.rb_node; >>>> + mutex_lock(&prime_fpriv->lock); >>>> + >>>> + rb = prime_fpriv->handles.rb_node; >>>> while (rb) { >>>> struct drm_prime_member *member; >>>> - member = rb_entry(rb, struct drm_prime_member, dmabuf_rb); >>>> - if (member->dma_buf == dma_buf) { >>>> + member = rb_entry(rb, struct drm_prime_member, handle_rb); >>>> + if (member->handle == handle) { >>>> rb_erase(&member->handle_rb, &prime_fpriv->handles); >>>> rb_erase(&member->dmabuf_rb, &prime_fpriv->dmabufs); >>>> - dma_buf_put(dma_buf); >>>> + dma_buf_put(member->dma_buf); >>>> kfree(member); >>>> - return; >>>> - } else if (member->dma_buf < dma_buf) { >>>> + break; >>>> + } else if (member->handle < handle) { >>>> rb = rb->rb_right; >>>> } else { >>>> rb = rb->rb_left; >>>> } >>>> } >>>> + >>>> + mutex_unlock(&prime_fpriv->lock); >>>> } >>>> void drm_prime_init_file_private(struct drm_prime_file_private >>>> *prime_fpriv) >>> >>> >> > >
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