Re: [PATCH 3/3] dmaengine: xilinx: dpdma: Reserve space for a string terminator

[Frank Li <Frank.li@oss.nxp.com>]

On Sat, Sep 26, 2026 at 05:34:15PM +0300, Laurent Pinchart wrote:
> On Sat, Sep 26, 2026 at 08:12:50PM +0800, Jiale Yao wrote:
> > xilinx_dpdma_debugfs_write() allocates a buffer of size bytes, and
> > strncpy_from_user() can fill it without a terminating NUL when the input
> > has no NUL in the copied range. strsep() and strcasecmp() then read
> > beyond the buffer.
>
> strncpy() has long been considered unsafe, and has finally been removed
> from the kernel in v7.2. A better fix would be to similarly replace
> strncpy_from_user() with a safe equivalent.

Do you means use strndup_user()?

Frank

>
> > Allocate an extra byte and keep that byte zero-initialized, so the input
> > copied remains unchanged and the buffer is always terminated.
> >
> > Fixes: 1d220435cab3 ("dmaengine: xilinx: dpdma: Add debugfs support")
> > Signed-off-by: Jiale Yao <yaojiale02@163.com>
> > ---
> >  drivers/dma/xilinx/xilinx_dpdma.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/dma/xilinx/xilinx_dpdma.c b/drivers/dma/xilinx/xilinx_dpdma.c
> > index d9a3542c4531..b61ef3062d84 100644
> > --- a/drivers/dma/xilinx/xilinx_dpdma.c
> > +++ b/drivers/dma/xilinx/xilinx_dpdma.c
> > @@ -410,7 +410,7 @@ static ssize_t xilinx_dpdma_debugfs_write(struct file *f,
> >  	if (dpdma_debugfs.testcase != DPDMA_TC_NONE)
> >  		return -EBUSY;
> >
> > -	kern_buff = kzalloc(size, GFP_KERNEL);
> > +	kern_buff = kzalloc(size + 1, GFP_KERNEL);
> >  	if (!kern_buff)
> >  		return -ENOMEM;
> >  	kern_buff_start = kern_buff;
>
> --
> Regards,
>
> Laurent Pinchart