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.
Cc: Alex Deucher alexander.deucher@amd.com Cc: Christian König christian.koenig@amd.com Cc: Chris Wilson chris@chris-wilson.co.uk Cc: Thomas Zimmermann tzimmermann@suse.de Cc: Rob Herring robh@kernel.org Cc: Tomeu Vizoso tomeu.vizoso@collabora.com Cc: Eric Anholt eric@anholt.net Cc: Dave Airlie airlied@redhat.com Cc: Gerd Hoffmann kraxel@redhat.com Cc: Ben Skeggs bskeggs@redhat.com Cc: "VMware Graphics" linux-graphics-maintainer@vmware.com Cc: Thomas Hellstrom thellstrom@vmware.com Signed-off-by: Daniel Vetter daniel.vetter@intel.com --- 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 42a8f3f11681..d233ef4cf0d7 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 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); + + mmput(mm); +} +subsys_initcall(dma_resv_lockdep); +#endif + /** * dma_resv_init - initialize a reservation object * @obj: the reservation object