On Wed, Dec 4, 2024 at 10:14 AM Kasireddy, Vivek <vivek.kasireddy@xxxxxxxxx> wrote: > > Subject: [PATCH 3/3] udmabuf: fix memory leak on last export_udmabuf() > > error path > > > > In export_udmabuf(), if dma_buf_fd() fails because the FD table is full, a > > dma_buf owning the udmabuf has already been created; but the error > > handling > > in udmabuf_create() will tear down the udmabuf without doing anything > > about > > the containing dma_buf. > > > > This leaves a dma_buf in memory that contains a dangling pointer; though > > that doesn't seem to lead to anything bad except a memory leak. > > > > Fix it by moving the dma_buf_fd() call out of export_udmabuf() so that we > > can give it different error handling. > > > > Note that the shape of this code changed a lot in commit 5e72b2b41a21 > > ("udmabuf: convert udmabuf driver to use folios"); but the memory leak > > seems to have existed since the introduction of udmabuf. > > > > Fixes: fbb0de795078 ("Add udmabuf misc device") > > Signed-off-by: Jann Horn <jannh@xxxxxxxxxx> [...] > > @@ -330,11 +329,7 @@ static int export_udmabuf(struct udmabuf *ubuf, > > exp_info.priv = ubuf; > > exp_info.flags = O_RDWR; > > > > - buf = dma_buf_export(&exp_info); > > - if (IS_ERR(buf)) > > - return PTR_ERR(buf); > > - > > - return dma_buf_fd(buf, flags); > flags is now unused in this function. Ack, will remove in v2. > > + return dma_buf_export(&exp_info); > > } > > > > static long udmabuf_pin_folios(struct udmabuf *ubuf, struct file *memfd, > > @@ -391,6 +386,7 @@ static long udmabuf_create(struct miscdevice > > *device, > > struct folio **folios = NULL; > > pgoff_t pgcnt = 0, pglimit; > > struct udmabuf *ubuf; > > + struct dma_buf *dmabuf; > > long ret = -EINVAL; > > u32 i, flags; > > > > @@ -451,9 +447,16 @@ static long udmabuf_create(struct miscdevice > > *device, > > } > > > > flags = head->flags & UDMABUF_FLAGS_CLOEXEC ? O_CLOEXEC : 0; > > - ret = export_udmabuf(ubuf, device, flags); > > - if (ret < 0) > > + dmabuf = export_udmabuf(ubuf, device, flags); > > + if (IS_ERR(dmabuf)) { > > + ret = PTR_ERR(dmabuf); > > goto err; > > + } > > + /* ownership of ubuf is held by the dmabuf from here */ > Please also add a comment here that says that if dma_buf_fd() fails, > then calling dma_buf_put() will enable cleanup to be done via release(). Ack, added in v2. > With that, > > Acked-by: Vivek Kasireddy <vivek.kasireddy@xxxxxxxxx> Thanks!