| Message ID | 20221121075618.15877-1-korotkov.maxim.s@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | ethtool: avoiding integer overflow in ethtool_phys_id() | expand |
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
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]. > > Andrew > [0] https://elixir.bootlin.com/linux/v6.1-rc6/source/include/linux/math64.h#L153 Thanks, Olek
On Mon, 21 Nov 2022 10:56:18 +0300 Maxim Korotkov wrote: > Found by Linux Verification Center (linuxtesting.org) with SVACE. > > Fixes: 2adc6edcaec0 ("ethtool: fix error handling in ethtool_phys_id") I'm leaning towards dropping the fixes tag, and applying to -next. Drivers returning high enough rc to cause an overflow seems theoretical, and is pretty harmless. Please LMK if I'm missing something.
> -----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
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
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; do { rtnl_lock();
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(-)