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Wed, 23 Jul 2025 10:55:51 -0700 (PDT) Date: Wed, 23 Jul 2025 10:55:48 -0700 From: Sultan Alsawaf To: Bin Du Cc: mchehab@kernel.org, hverkuil@xs4all.nl, laurent.pinchart+renesas@ideasonboard.com, bryan.odonoghue@linaro.org, sakari.ailus@linux.intel.com, prabhakar.mahadev-lad.rj@bp.renesas.com, linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, pratap.nirujogi@amd.com, benjamin.chan@amd.com, king.li@amd.com, gjorgji.rosikopulos@amd.com, Phil.Jawich@amd.com, Dominic.Antony@amd.com, Svetoslav.Stoilov@amd.com Subject: Re: [PATCH v2 6/8] media: platform: amd: isp4 video node and buffers handling added Message-ID: References: <20250618091959.68293-1-Bin.Du@amd.com> <20250618091959.68293-7-Bin.Du@amd.com> Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250618091959.68293-7-Bin.Du@amd.com> On Wed, Jun 18, 2025 at 05:19:57PM +0800, Bin Du wrote: > +static void isp4vid_vb2_detach_dmabuf(void *mem_priv) > +{ > + struct isp4vid_vb2_buf *buf = mem_priv; > + > + if (!buf) { > + pr_err("fail invalid buf handle\n"); > + return; > + } > + > + struct iosys_map map = IOSYS_MAP_INIT_VADDR(buf->vaddr); Variable declaration mixed with code, move the variable declaration to the top. > + > + dev_dbg(buf->dev, "detach dmabuf of isp user bo 0x%llx size %ld", > + buf->gpu_addr, buf->size); > + > + if (buf->vaddr) > + dma_buf_vunmap_unlocked(buf->dbuf, &map); > + > + // put dmabuf for exported ones > + dma_buf_put(buf->dbuf); The dmabuf shouldn't be put from the detach_dmabuf memop. Remove this. > + > + kfree(buf); > +} [snip] > +static void isp4vid_vb2_dmabuf_ops_release(struct dma_buf *dbuf) > +{ > + struct isp4vid_vb2_buf *buf = dbuf->priv; > + > + /* drop reference obtained in vb2_isp4vid_get_dmabuf */ s/vb2_isp4vid_get_dmabuf/isp4vid_vb2_get_dmabuf/ > + if (buf->is_expbuf) > + isp4vid_vb2_put(dbuf->priv); > + else > + dev_dbg(buf->dev, "ignore buf release for implicit case"); > +} [snip] > +static struct dma_buf *isp4vid_vb2_get_dmabuf(struct vb2_buffer *vb, > + void *buf_priv, > + unsigned long flags) > +{ > + struct isp4vid_vb2_buf *buf = buf_priv; > + struct dma_buf *dbuf; > + > + if (buf->dbuf) { > + dev_dbg(buf->dev, > + "dbuf already created, reuse implicit dbuf\n"); > + dbuf = buf->dbuf; The dmabuf is reused here without taking a reference to it. When the get_dmabuf memop is called by vb2_core_expbuf(), it assumes that a reference to the dmabuf is acquired. So you need to add `get_dma_buf(dbuf)` here. > + } else { > + dbuf = isp4vid_get_dmabuf(vb, buf_priv, flags); > + dev_dbg(buf->dev, "created new dbuf\n"); > + } > + buf->is_expbuf = true; > + refcount_inc(&buf->refcount); > + > + dev_dbg(buf->dev, "buf exported, refcount %d\n", > + buf->refcount.refs.counter); > + > + return dbuf; > +} [snip] > +static void *isp4vid_vb2_get_userptr(struct vb2_buffer *vb, struct device *dev, > + unsigned long vaddr, unsigned long size) > +{ > + struct isp4vid_vb2_buf *buf; > + struct frame_vector *vec; > + int n_pages, offset, i; > + int ret = -ENOMEM; > + > + buf = kzalloc(sizeof(*buf), GFP_KERNEL); > + if (!buf) > + return ERR_PTR(-ENOMEM); > + > + buf->dev = dev; > + buf->dma_dir = vb->vb2_queue->dma_dir; > + offset = vaddr & ~PAGE_MASK; > + buf->size = size; > + vec = vb2_create_framevec(vaddr, size, > + buf->dma_dir == DMA_FROM_DEVICE || > + buf->dma_dir == DMA_BIDIRECTIONAL); > + if (IS_ERR(vec)) { > + kfree(buf); > + return vec; > + } You can combine the error handling here with the error path at the bottom of the function instead of duplicating the `kfree(buf)`. > + buf->vec = vec; > + n_pages = frame_vector_count(vec); > + if (frame_vector_to_pages(vec) < 0) { > + unsigned long *nums = frame_vector_pfns(vec); > + > + /* > + * We cannot get page pointers for these pfns. Check memory is > + * physically contiguous and use direct mapping. > + */ > + for (i = 1; i < n_pages; i++) > + if (nums[i - 1] + 1 != nums[i]) > + goto err_destroy_free; > + buf->vaddr = (__force void *) > + ioremap(__pfn_to_phys(nums[0]), size + offset); > + } else { > + buf->vaddr = vm_map_ram(frame_vector_pages(vec), n_pages, -1); > + } > + > + if (!buf->vaddr) > + goto err_destroy_free; > + > + buf->vaddr = ((char *)buf->vaddr) + offset; > + return buf; > + > +err_destroy_free: > + vb2_destroy_framevec(vec); > + kfree(buf); > + return ERR_PTR(ret); > +} > + > +static void isp4vid_vb2_put(void *buf_priv) > +{ > + struct isp4vid_vb2_buf *buf = (struct isp4vid_vb2_buf *)buf_priv; > + struct amdgpu_bo *bo = (struct amdgpu_bo *)buf->bo; > + > + dev_dbg(buf->dev, > + "release isp user bo 0x%llx size %ld refcount %d is_expbuf %d", > + buf->gpu_addr, buf->size, > + buf->refcount.refs.counter, buf->is_expbuf); > + > + if (refcount_dec_and_test(&buf->refcount)) { > + amdgpu_bo_free_isp_user(bo); > + > + // put implicit dmabuf here, detach_dmabuf will not be called Comment style (use /**/ instead of //). > + if (!buf->is_expbuf) > + dma_buf_put(buf->dbuf); > + > + vfree(buf->vaddr); > + kfree(buf); > + buf = NULL; `buf = NULL;` here is superfluous; you can remove it. > + } else { > + dev_warn(buf->dev, "ignore buffer free, refcount %u > 0", > + refcount_read(&buf->refcount)); This refcount_read() is a possible use-after-free because `buf` is accessed after isp4vid_vb2_put() puts its reference to `buf`. So something else could put the last reference to `buf` and free it after this refcount dec but before the refcount_read(). Maybe just remove this dev_warn() entirely? > + } > +} > + > +static void *isp4vid_vb2_alloc(struct vb2_buffer *vb, struct device *dev, > + unsigned long size) > +{ > + struct isp4vid_dev *isp_vdev = vb2_get_drv_priv(vb->vb2_queue); > + struct isp4vid_vb2_buf *buf = NULL; > + struct amdgpu_bo *bo; > + u64 gpu_addr; > + u32 ret; > + > + buf = kzalloc(sizeof(*buf), GFP_KERNEL | vb->vb2_queue->gfp_flags); > + if (!buf) > + return ERR_PTR(-ENOMEM); > + > + buf->dev = dev; > + buf->size = size; > + buf->vaddr = vmalloc_user(buf->size); > + if (!buf->vaddr) { > + kfree(buf); > + return ERR_PTR(-ENOMEM); > + } > + > + buf->dma_dir = vb->vb2_queue->dma_dir; > + buf->handler.refcount = &buf->refcount; > + buf->handler.put = isp4vid_vb2_put; > + buf->handler.arg = buf; What is buf->handler for? I don't see it used anywhere in the entire patchset; I can delete `handler` from `struct isp4vid_vb2_buf` along with these lines and it compiles. > + > + // get implicit dmabuf Comment style. > + buf->dbuf = isp4vid_get_dmabuf(vb, buf, 0); > + if (!buf->dbuf) { > + dev_err(dev, "fail to get dmabuf\n"); > + return ERR_PTR(-EINVAL); > + } Doesn't free `buf` or `buf->vaddr` on error here. Also, comment style. > + > + // create isp user BO and obtain gpu_addr Comment style. > + ret = amdgpu_bo_create_isp_user(isp_vdev->amdgpu_dev, buf->dbuf, > + AMDGPU_GEM_DOMAIN_GTT, &bo, &gpu_addr); > + if (ret) { > + dev_err(dev, "fail to create BO\n"); > + return ERR_PTR(-EINVAL); > + } Doesn't free `buf` or `buf->vaddr` or put `buf->dbuf` on error here. > + > + buf->bo = (void *)bo; > + buf->gpu_addr = gpu_addr; > + > + refcount_set(&buf->refcount, 1); This discards the refcount inc triggered from amdgpu_bo_create_isp_user() when it calls get_dma_buf(), leading to a use-after-free. Move this refcount_set() up, preferably right after vmalloc_user() or right after `buf` is allocated so there's no risk of this issue occurring again in the future. > + > + dev_dbg(dev, "allocated isp user bo 0x%llx size %ld refcount %d", > + buf->gpu_addr, buf->size, buf->refcount.refs.counter); > + > + return buf; > +} [snip] Sultan