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Message-ID: <f6deb4f4ebc0659dfdb011c7aec5e4c792f3ef49.camel@redhat.com> Date: Tue, 30 May 2023 11:40:56 +0200 From: Paolo Abeni <pabeni@...hat.com> To: Dan Carpenter <dan.carpenter@...aro.org> Cc: Jakub Kicinski <kuba@...nel.org>, Andrew Lunn <andrew@...n.ch>, Russell King <linux@...linux.org.uk>, Oleksij Rempel <linux@...pel-privat.de>, Heiner Kallweit <hkallweit1@...il.com>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.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, 2023-05-30 at 12:23 +0300, Dan Carpenter wrote: > On Tue, May 30, 2023 at 11:06:55AM +0200, Paolo Abeni wrote: > > On Mon, 2023-05-29 at 21:58 -0700, Jakub Kicinski wrote: > > > On Fri, 26 May 2023 14:45:54 +0300 Dan Carpenter wrote: > > > > The "val" variable is used to store error codes from phy_read() so > > > > it needs to be signed for the error handling to work as expected. > > > > > > > > Fixes: 014068dcb5b1 ("net: phy: genphy_loopback: add link speed configuration") > > > > Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org> > > > > > > Is it going to be obvious to PHY-savvy folks that the val passed to > > > phy_read_poll_timeout() must be an int? Is it a very common pattern? > > > My outsider intuition is that since regs are 16b, u16 is reasonable, > > > and more people may make the same mistake. Therefore we should try to > > > fix phy_read_poll_timeout() instead to use a local variable like it > > > does for __ret. > > > > > > Weaker version would be to add a compile time check to ensure val > > > is signed (assert(typeof(val)~0ULL < 0) or such?). > > > > FTR, a BUILD_BUG_ON() the above check spots issues in several places > > (e.g. r8169_main.c, drivers/net/phy/phy_device.c, ...) > > > > I don't see an issue in r8169_main.c and in drivers/net/phy/phy_device.c > then I only find the bug from this patch. > > regards, > dan carpenter > > diff --git a/include/linux/phy.h b/include/linux/phy.h > index 6478838405a08..f05fc25b77583 100644 > --- a/include/linux/phy.h > +++ b/include/linux/phy.h > @@ -1173,6 +1173,7 @@ static inline int phy_read(struct phy_device *phydev, u32 regnum) > ({ \ > int __ret = read_poll_timeout(phy_read, val, val < 0 || (cond), \ > sleep_us, timeout_us, sleep_before_read, phydev, regnum); \ > + BUILD_BUG_ON((typeof(val))~0ULL > 0); \ > if (val < 0) \ > __ret = val; \ > if (__ret) \ > Uhm... I have no idea what happened to my build host. I did see more build errors in previous attempt, but now I only observe the one you address with this patch. I guess some PEBKAC hit me here. /P
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