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Wed, 10 Feb 2021 02:48:43 -0800 (PST) Date: Wed, 10 Feb 2021 16:18:28 +0530 From: Amey Narkhede To: Dan Carpenter Cc: devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org Subject: Re: [PATCH v2] staging: gdm724x: Fix DMA from stack Message-ID: <20210210104828.5kmdhrt6kaglmlmv@archlinux> References: <20210210080134.1978-1-ameynarkhede03@gmail.com> <20210210085811.7dunnfly6cqw67m3@archlinux> <20210210090442.GV2696@kadam> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="knuynokjtvzjzo4t" Content-Disposition: inline In-Reply-To: <20210210090442.GV2696@kadam> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --knuynokjtvzjzo4t Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On 21/02/10 12:04PM, Dan Carpenter wrote: > On Wed, Feb 10, 2021 at 02:28:11PM +0530, Amey Narkhede wrote: > > On 21/02/10 09:06AM, Greg KH wrote: > > > On Wed, Feb 10, 2021 at 01:31:34PM +0530, Amey Narkhede wrote: > > > > Stack allocated buffers cannot be used for DMA > > > > on all architectures so allocate hci_packet buffer > > > > using kzalloc(). > > > > > > > > Signed-off-by: Amey Narkhede > > > > --- > > > > Changes in v2: > > > > - Fixed build warning > > > > - Fixed memory leak using kfree > > > > > > > > drivers/staging/gdm724x/gdm_usb.c | 9 +++++++-- > > > > 1 file changed, 7 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/drivers/staging/gdm724x/gdm_usb.c b/drivers/staging/gdm724x/gdm_usb.c > > > > index dc4da66c3..c4a9b90c5 100644 > > > > --- a/drivers/staging/gdm724x/gdm_usb.c > > > > +++ b/drivers/staging/gdm724x/gdm_usb.c > > > > @@ -56,11 +56,15 @@ static int gdm_usb_recv(void *priv_dev, > > > > > > > > static int request_mac_address(struct lte_udev *udev) > > > > { > > > > - u8 buf[16] = {0,}; > > > > - struct hci_packet *hci = (struct hci_packet *)buf; > > > > + u8 *buf; > > > > + struct hci_packet *hci; > > > > struct usb_device *usbdev = udev->usbdev; > > > > int actual; > > > > int ret = -1; > > > > + buf = kzalloc(16, GFP_KERNEL); > > > > > > checkpatch did not complain about this? > > No. checkpatch shows no errors and warnings. > > > > > > And why do you need 'buf' anymore now? Why not just allocate hci and > > > pass that to the request instead? Saves you an extra cast and an extra > > > pointer. > > > > > > thanks, > > > > > > greg k-h > > Thanks. I'll send v3. I assume now we don't need kzalloc anymore as we initialize > > the hci_packet so kmalloc(sizeof(struct hci_packet),..) will do. > > We only initialize the first five bytes, but it also seems as if we only > use the first five bytes which raises the question of why we are > allocating 16 bytes. > > regards, > dan carpenter > That makes sense. I kept 16 bytes as original implementation allocated 16 bytes on stack. 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