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Message-ID: <813008f6-cb26-4666-81ca-6f88c04bba07@kili.mountain> Date: Tue, 30 May 2023 12:23:32 +0300 From: Dan Carpenter <dan.carpenter@...aro.org> To: Paolo Abeni <pabeni@...hat.com> 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, 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) \
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