Hi Jann,
> 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>
> ---
> drivers/dma-buf/udmabuf.c | 25 ++++++++++++++-----------
> 1 file changed, 14 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
> index
> 8ce77f5837d71a73be677cad014e05f29706057d..aae0071be14a2c83a428b59
> ea9e905c7173232be 100644
> --- a/drivers/dma-buf/udmabuf.c
> +++ b/drivers/dma-buf/udmabuf.c
> @@ -317,12 +317,11 @@ static int check_memfd_seals(struct file *memfd)
> return 0;
> }
>
> -static int export_udmabuf(struct udmabuf *ubuf,
> - struct miscdevice *device,
> - u32 flags)
> +static struct dma_buf *export_udmabuf(struct udmabuf *ubuf,
> + struct miscdevice *device,
> + u32 flags)
> {
> DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
> - struct dma_buf *buf;
>
> ubuf->device = device;
> exp_info.ops = &udmabuf_ops;
> @@ -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.
> + 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().
With that,
Acked-by: Vivek Kasireddy <vivek.kasireddy@xxxxxxxxx>
> +
> + ret = dma_buf_fd(dmabuf, flags);
> + if (ret < 0)
> + dma_buf_put(dmabuf);
>
> kvfree(folios);
> return ret;
>
> --
> 2.47.0.338.g60cca15819-goog
