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Tue, 26 May 2026 02:59:03 -0700 (PDT) Received: from localhost ([196.207.164.177]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49044f2bad3sm339178815e9.0.2026.05.26.02.59.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 May 2026 02:59:02 -0700 (PDT) Date: Tue, 26 May 2026 12:58:59 +0300 From: Dan Carpenter To: Angelo Dureghello , Nuno =?iso-8859-1?Q?S=E1?= , Michael Hennerich , Jonathan Cameron , David Lechner , Andy Shevchenko , linux@analog.com, linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org Subject: Re: [PATCH] iio: dac: ad3552r-hs: fix uninitialized data ni ad3552r_hs_write_data_source() Message-ID: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, May 25, 2026 at 01:11:42AM -0700, Angelo Dureghello wrote: > Hi Dan, > > On Mon, May 25, 2026 at 10:15:46AM +0300, Dan Carpenter wrote: > > If the *ppos value is non-zero then the simple_write_to_buffer() function > > won't initialized the start of the buf[] buffer. Non-zero values for > > *ppos won't work here generally, so just test for them and return -EINVAL > > at the start of the function. > > > > Fixes: b1c5d68ea66e ("iio: dac: ad3552r-hs: add support for internal ramp") > > Signed-off-by: Dan Carpenter > > --- > > drivers/iio/dac/ad3552r-hs.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/iio/dac/ad3552r-hs.c b/drivers/iio/dac/ad3552r-hs.c > > index a9578afa7015..6bc64f53bce9 100644 > > --- a/drivers/iio/dac/ad3552r-hs.c > > +++ b/drivers/iio/dac/ad3552r-hs.c > > @@ -549,7 +549,7 @@ static ssize_t ad3552r_hs_write_data_source(struct file *f, > > > > guard(mutex)(&st->lock); > > > > - if (count >= sizeof(buf)) > > + if (*ppos != 0 || count >= sizeof(buf)) > > return -ENOSPC; > > > > ret = simple_write_to_buffer(buf, sizeof(buf) - 1, ppos, userbuf, > > -- > > thanks for the fix, > > Reviewed-by: Angelo Dureghello > > it looks like this may fix an additional overflow in case ppos is near the > end of buf[]. simple_write_to_buffer() won't overflow. It takes ppos into consideration properly. > But i am actually missing the use case when ppos is non zero, can this > happen from shell "echo" ? Or some fseek/dd is needed to trigger it ? I've never actually tried to do this. I think lseek() or fseek() would work. But also the simple_write_to_buffer() function itself updates *ppos so multiple writes would do the trick as well. regards, dan carpenter