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Message-ID: <ZHZQ+1KNGB7KYZGi@shell.armlinux.org.uk> Date: Tue, 30 May 2023 20:39:39 +0100 From: "Russell King (Oracle)" <linux@...linux.org.uk> To: Jakub Kicinski <kuba@...nel.org> Cc: Andrew Lunn <andrew@...n.ch>, Dan Carpenter <dan.carpenter@...aro.org>, Oleksij Rempel <linux@...pel-privat.de>, Heiner Kallweit <hkallweit1@...il.com>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, kernel-janitors@...r.kernel.org Subject: Re: [PATCH net] net: phy: fix a signedness bug in genphy_loopback() On Tue, May 30, 2023 at 12:19:10PM -0700, Jakub Kicinski wrote: > On Tue, 30 May 2023 14:39:53 +0200 Andrew Lunn wrote: > > > Therefore we should try to fix phy_read_poll_timeout() instead to > > > use a local variable like it does for __ret. > > > > The problem with that is val is supposed to be available to the > > caller. I don't know if it is every actually used, but if it is, using > > an internal signed variable and then throwing away the sign bit on > > return is going to result in similar bugs. > > This is what I meant FWIW: > > diff --git a/include/linux/phy.h b/include/linux/phy.h > index 7addde5d14c0..829bd57b8794 100644 > --- a/include/linux/phy.h > +++ b/include/linux/phy.h > @@ -1206,10 +1206,13 @@ static inline int phy_read(struct phy_device *phydev, u32 regnum) > #define phy_read_poll_timeout(phydev, regnum, val, cond, sleep_us, \ > timeout_us, sleep_before_read) \ > ({ \ > - int __ret = read_poll_timeout(phy_read, val, val < 0 || (cond), \ > + int __ret, __val; \ > + \ > + __ret = read_poll_timeout(phy_read, __val, __val < 0 || (cond), \ > sleep_us, timeout_us, sleep_before_read, phydev, regnum); \ > - if (val < 0) \ > - __ret = val; \ > + val = __val; > + if (__val < 0) \ > + __ret = __val; \ > if (__ret) \ > phydev_err(phydev, "%s failed: %d\n", __func__, __ret); \ > __ret; \ > > > I tried enabling -Wtype-limits but it's _very_ noisy :( Yes, looks good, that's what I thought you were meaning, and I totally agree with it. Thanks! Whatever we decide for this will also need to be applied to phy_read_mmd_poll_timeout() as well. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!
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