[PATCH] dmabuf: fix NULL pointer dereference in dma_buf_release()

[PATCH] dmabuf: fix NULL pointer dereference in dma_buf_release()

[Charan Teja Reddy]

NULL pointer dereference is observed while exporting the dmabuf but
failed to allocate the 'struct file' which results into the dropping of
the allocated dentry corresponding to this file in the dmabuf fs, which
is ending up in dma_buf_release() and accessing the uninitialzed
dentry->d_fsdata.

Call stack on 5.4 is below:
 dma_buf_release+0x2c/0x254 drivers/dma-buf/dma-buf.c:88
 __dentry_kill+0x294/0x31c fs/dcache.c:584
 dentry_kill fs/dcache.c:673 [inline]
 dput+0x250/0x380 fs/dcache.c:859
 path_put+0x24/0x40 fs/namei.c:485
 alloc_file_pseudo+0x1a4/0x200 fs/file_table.c:235
 dma_buf_getfile drivers/dma-buf/dma-buf.c:473 [inline]
 dma_buf_export+0x25c/0x3ec drivers/dma-buf/dma-buf.c:585

Fix this by checking for the valid pointer in the dentry->d_fsdata.

Fixes: 4ab59c3c638c ("dma-buf: Move dma_buf_release() from fops to dentry_ops")
Cc: <stable@vger.kernel.org> [5.7+]
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>
---
 drivers/dma-buf/dma-buf.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 58564d82..844967f 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -59,6 +59,8 @@ static void dma_buf_release(struct dentry *dentry)
 	struct dma_buf *dmabuf;
 
 	dmabuf = dentry->d_fsdata;
+	if (unlikely(!dmabuf))
+		return;
 
 	BUG_ON(dmabuf->vmapping_counter);
 
-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member of the Code Aurora Forum, hosted by The Linux Foundation

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Re: [PATCH] dmabuf: fix NULL pointer dereference in dma_buf_release()

[Christian König]

Am 18.09.20 um 12:32 schrieb Charan Teja Reddy:
> NULL pointer dereference is observed while exporting the dmabuf but
> failed to allocate the 'struct file' which results into the dropping of
> the allocated dentry corresponding to this file in the dmabuf fs, which
> is ending up in dma_buf_release() and accessing the uninitialzed
> dentry->d_fsdata.
>
> Call stack on 5.4 is below:
>   dma_buf_release+0x2c/0x254 drivers/dma-buf/dma-buf.c:88
>   __dentry_kill+0x294/0x31c fs/dcache.c:584
>   dentry_kill fs/dcache.c:673 [inline]
>   dput+0x250/0x380 fs/dcache.c:859
>   path_put+0x24/0x40 fs/namei.c:485
>   alloc_file_pseudo+0x1a4/0x200 fs/file_table.c:235
>   dma_buf_getfile drivers/dma-buf/dma-buf.c:473 [inline]
>   dma_buf_export+0x25c/0x3ec drivers/dma-buf/dma-buf.c:585
>
> Fix this by checking for the valid pointer in the dentry->d_fsdata.
>
> Fixes: 4ab59c3c638c ("dma-buf: Move dma_buf_release() from fops to dentry_ops")
> Cc: <stable@vger.kernel.org> [5.7+]
> Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>

Reviewed-by: Christian König <christian.koenig@amd.com>

Going to pick this up for inclusion into drm-misc-next as well.

> ---
>   drivers/dma-buf/dma-buf.c | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index 58564d82..844967f 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -59,6 +59,8 @@ static void dma_buf_release(struct dentry *dentry)
>   	struct dma_buf *dmabuf;
>   
>   	dmabuf = dentry->d_fsdata;
> +	if (unlikely(!dmabuf))
> +		return;
>   
>   	BUG_ON(dmabuf->vmapping_counter);
>   

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Re: [PATCH] dmabuf: fix NULL pointer dereference in dma_buf_release()

[Daniel Vetter]

On Fri, Sep 18, 2020 at 01:16:16PM +0200, Christian König wrote:
> Am 18.09.20 um 12:32 schrieb Charan Teja Reddy:
> > NULL pointer dereference is observed while exporting the dmabuf but
> > failed to allocate the 'struct file' which results into the dropping of
> > the allocated dentry corresponding to this file in the dmabuf fs, which
> > is ending up in dma_buf_release() and accessing the uninitialzed
> > dentry->d_fsdata.
> > 
> > Call stack on 5.4 is below:
> >   dma_buf_release+0x2c/0x254 drivers/dma-buf/dma-buf.c:88
> >   __dentry_kill+0x294/0x31c fs/dcache.c:584
> >   dentry_kill fs/dcache.c:673 [inline]
> >   dput+0x250/0x380 fs/dcache.c:859
> >   path_put+0x24/0x40 fs/namei.c:485
> >   alloc_file_pseudo+0x1a4/0x200 fs/file_table.c:235
> >   dma_buf_getfile drivers/dma-buf/dma-buf.c:473 [inline]
> >   dma_buf_export+0x25c/0x3ec drivers/dma-buf/dma-buf.c:585
> > 
> > Fix this by checking for the valid pointer in the dentry->d_fsdata.
> > 
> > Fixes: 4ab59c3c638c ("dma-buf: Move dma_buf_release() from fops to dentry_ops")
> > Cc: <stable@vger.kernel.org> [5.7+]
> > Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>
> 
> Reviewed-by: Christian König <christian.koenig@amd.com>
> 
> Going to pick this up for inclusion into drm-misc-next as well.

drm-misc-fixes since this is a bugfix that needs to be backported.
-Daniel

> 
> > ---
> >   drivers/dma-buf/dma-buf.c | 2 ++
> >   1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> > index 58564d82..844967f 100644
> > --- a/drivers/dma-buf/dma-buf.c
> > +++ b/drivers/dma-buf/dma-buf.c
> > @@ -59,6 +59,8 @@ static void dma_buf_release(struct dentry *dentry)
> >   	struct dma_buf *dmabuf;
> >   	dmabuf = dentry->d_fsdata;
> > +	if (unlikely(!dmabuf))
> > +		return;
> >   	BUG_ON(dmabuf->vmapping_counter);
> 
> _______________________________________________
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> dri-devel@lists.freedesktop.org
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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