Messages in this thread | | | Date | Tue, 22 Nov 2022 09:53:48 +0300 | Subject | Re: [PATCH] ethtool: avoiding integer overflow in ethtool_phys_id() | From | Maxim Korotkov <> |
| |
Ok, I'll replace cast to macro in patch V2
On 22.11.2022 00:30, Keller, Jacob E wrote: > > >> -----Original Message----- >> From: Alexander Lobakin <alexandr.lobakin@intel.com> >> Sent: Monday, November 21, 2022 7:03 AM >> To: Andrew Lunn <andrew@lunn.ch> >> Cc: Lobakin, Alexandr <alexandr.lobakin@intel.com>; Maxim Korotkov >> <korotkov.maxim.s@gmail.com>; David S. Miller <davem@davemloft.net>; Eric >> Dumazet <edumazet@google.com>; Jakub Kicinski <kuba@kernel.org>; Paolo >> Abeni <pabeni@redhat.com>; Guangbin Huang >> <huangguangbin2@huawei.com>; Tom Rix <trix@redhat.com>; Marco Bonelli >> <marco@mebeim.net>; Edward Cree <ecree@solarflare.com>; >> netdev@vger.kernel.org; linux-kernel@vger.kernel.org; lvc- >> project@linuxtesting.org >> Subject: Re: [PATCH] ethtool: avoiding integer overflow in ethtool_phys_id() >> >> From: Andrew Lunn <andrew@lunn.ch> >> Date: Mon, 21 Nov 2022 15:10:18 +0100 >> >>> 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. >> >> This particular one is absolutely fine. When you want to multiply >> u32 by u32, you always need a cast, otherwise the result will be >> truncated. mul_u32_u32() does it the very same way[0]. >> > > Why not just use mul_u32_u32 then? > > Thanks, > Jake > >>> >>> Andrew >>> >> >> [0] https://elixir.bootlin.com/linux/v6.1- >> rc6/source/include/linux/math64.h#L153 >> >> Thanks, >> Olek
| |