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Mon, 20 Jan 2025 22:48:30 -0800 (PST) Received: from grain.localdomain ([5.18.253.97]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-437c753c617sm227775455e9.37.2025.01.20.22.48.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Jan 2025 22:48:30 -0800 (PST) Received: by grain.localdomain (Postfix, from userid 1000) id 263F45A003F; Tue, 21 Jan 2025 09:48:28 +0300 (MSK) Date: Tue, 21 Jan 2025 09:48:28 +0300 From: Cyrill Gorcunov To: Thomas =?iso-8859-1?Q?Wei=DFschuh?= Cc: LKML , Anna-Maria Behnsen , Frederic Weisbecker , Thomas Gleixner Subject: Re: [PATCH] posix-clock: drop code duplication using compat_ptr_ioctl Message-ID: References: <4229b992-77ef-404d-b045-8f1ccad1035a@t-8ch.de> <31acd2d0-8384-4ec5-acaa-187323b1968d@t-8ch.de> 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=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <31acd2d0-8384-4ec5-acaa-187323b1968d@t-8ch.de> User-Agent: Mutt/2.2.13 (2024-03-09) On Mon, Jan 20, 2025 at 11:41:26PM +0100, Thomas Weißschuh wrote: > > > > > +#ifdef CONFIG_COMPAT > > > +long ptp_compat_ioctl(struct posix_clock_context *pccontext, unsigned int cmd, > > > + unsigned long arg) > > > +{ > > > + switch (cmd) { > > > + case PTP_ENABLE_PPS: > > > + case PTP_ENABLE_PPS2: > > > + /* These take in scalar arg, do not convert */ > > > + break; > > > + default: > > > + arg = (unsigned long)compat_ptr(arg); > > > > Here^^^ Hi Thomas! > > The key is to only call compat_ptr() on *pointers*. > Scalars have to be passed through unmodified. > For ptp_ioctl(), PTP_ENABLE_PPS and PTP_ENABLE_PPS2 take such scalars, > which is why those two *can not* use compat_ptr(). > compat_ptr_ioctl() however passes all arguments through compat_ptr(). Yeah, and the PTP_ENABLE_PPS/PTP_ENABLE_PPS2 consider `arg` as 0/1 flip-flop so compat_ptr won't screw it. So I personally would rather stick with a more simple code (taking into account that ptp is the only real underlied device so far sitting in code for so long). > > Admittedly it's quite unlikely anybody would pass a value where it would > make a difference in practice. But if we fix this now, it might as well > be correct. Sure, I see your point. Thanks for comments! Cyrill