Messages in this thread | | | Date | Mon, 21 Nov 2022 15:10:18 +0100 | From | Andrew Lunn <> | Subject | Re: [PATCH] ethtool: avoiding integer overflow in ethtool_phys_id() |
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On Mon, Nov 21, 2022 at 10:56:18AM +0300, Maxim Korotkov wrote: > The value of an arithmetic expression "n * id.data" is subject > to possible overflow due to a failure to cast operands to a larger data > type before performing arithmetic. Added cast of first operand to u64 > for avoiding overflow. > > Found by Linux Verification Center (linuxtesting.org) with SVACE. > > Fixes: 2adc6edcaec0 ("ethtool: fix error handling in ethtool_phys_id") > Signed-off-by: Maxim Korotkov <korotkov.maxim.s@gmail.com> > --- > net/ethtool/ioctl.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c > index 6a7308de192d..cf87e53c2e74 100644 > --- a/net/ethtool/ioctl.c > +++ b/net/ethtool/ioctl.c > @@ -2007,7 +2007,7 @@ static int ethtool_phys_id(struct net_device *dev, void __user *useraddr) > } else { > /* Driver expects to be called at twice the frequency in rc */ > int n = rc * 2, interval = HZ / n; > - u64 count = n * id.data, i = 0; > + u64 count = (u64)n * id.data, i = 0;
How about moving the code around a bit, change n to a u64 and drop the cast? Does this look correct?
int interval = HZ / rc / 2; u64 n = rc * 2; u64 count = n * id.data;
i = 0;
I just don't like casts, they suggest the underlying types are wrong, so should fix that, not add a cast.
Andrew
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