[PATCH v2] core: dev: don't call BUG() on bad input

[PATCH v2] core: dev: don't call BUG() on bad input

[Vasiliy Kulikov]

alloc_netdev() may be called with too long name (more that IFNAMSIZ bytes).
Currently this leads to BUG().  Other insane inputs (bad txqs, rxqs) and
even OOM don't lead to BUG().  Made alloc_netdev() return NULL, like on
other errors.

Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
---
 Compile tested.
 v2 - fixed checkpatch warning - space before "\n".

 net/core/dev.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 6392ea0..12ef4b0 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5761,7 +5761,10 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
 	size_t alloc_size;
 	struct net_device *p;
 
-	BUG_ON(strlen(name) >= sizeof(dev->name));
+	if (strnlen(name, sizeof(dev->name)) >= sizeof(dev->name)) {
+		pr_err("alloc_netdev: Too long device name\n");
+		return NULL;
+	}
 
 	if (txqs < 1) {
 		pr_err("alloc_netdev: Unable to allocate device "
-- 
1.7.0.4

Re: [PATCH v2] core: dev: don't call BUG() on bad input

[Alexey Dobriyan]

On Mon, Feb 14, 2011 at 4:42 PM, Vasiliy Kulikov <segoon@openwall.com> wrote:
> alloc_netdev() may be called with too long name (more that IFNAMSIZ bytes).
> Currently this leads to BUG().  Other insane inputs (bad txqs, rxqs) and
> even OOM don't lead to BUG().  Made alloc_netdev() return NULL, like on
> other errors.

> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -5761,7 +5761,10 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
>        size_t alloc_size;
>        struct net_device *p;
>
> -       BUG_ON(strlen(name) >= sizeof(dev->name));
> +       if (strnlen(name, sizeof(dev->name)) >= sizeof(dev->name)) {
> +               pr_err("alloc_netdev: Too long device name\n");
> +               return NULL;
> +       }

Netdevice name isn't some random junk you get from userspace, so BUG is fine.

Re: [PATCH v2] core: dev: don't call BUG() on bad input

[Vasiliy Kulikov]

Alexey,

On Mon, Feb 14, 2011 at 17:16 +0200, Alexey Dobriyan wrote:
> On Mon, Feb 14, 2011 at 4:42 PM, Vasiliy Kulikov <segoon@openwall.com> wrote:
> > alloc_netdev() may be called with too long name (more that IFNAMSIZ bytes).
> > Currently this leads to BUG().  Other insane inputs (bad txqs, rxqs) and
> > even OOM don't lead to BUG().  Made alloc_netdev() return NULL, like on
> > other errors.
> 
> > --- a/net/core/dev.c
> > +++ b/net/core/dev.c
> > @@ -5761,7 +5761,10 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
> >        size_t alloc_size;
> >        struct net_device *p;
> >
> > -       BUG_ON(strlen(name) >= sizeof(dev->name));
> > +       if (strnlen(name, sizeof(dev->name)) >= sizeof(dev->name)) {
> > +               pr_err("alloc_netdev: Too long device name\n");
> > +               return NULL;
> > +       }
> 
> Netdevice name isn't some random junk you get from userspace, so BUG is fine.

It IS for bluetooth, see net/bluetooth/bnep/core.c: bnep_add_connection() and
net/bluetooth/bnep/sock.c: bnep_sock_ioctl(). 

And txqs, txqs?  Then why do not BUG() on bad txqs too?  Why so
insonsistent?  BUG() should be called in some critical situation, net
device creation is probably not such a thing.


Thanks,

-- 
Vasiliy Kulikov
http://www.openwall.com - bringing security into open computing environments

Re: [PATCH v2] core: dev: don't call BUG() on bad input

[Patrick McHardy]

Am 14.02.2011 16:16, schrieb Alexey Dobriyan:
> On Mon, Feb 14, 2011 at 4:42 PM, Vasiliy Kulikov <segoon@openwall.com> wrote:
>> alloc_netdev() may be called with too long name (more that IFNAMSIZ bytes).
>> Currently this leads to BUG().  Other insane inputs (bad txqs, rxqs) and
>> even OOM don't lead to BUG().  Made alloc_netdev() return NULL, like on
>> other errors.
> 
>> --- a/net/core/dev.c
>> +++ b/net/core/dev.c
>> @@ -5761,7 +5761,10 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
>>        size_t alloc_size;
>>        struct net_device *p;
>>
>> -       BUG_ON(strlen(name) >= sizeof(dev->name));
>> +       if (strnlen(name, sizeof(dev->name)) >= sizeof(dev->name)) {
>> +               pr_err("alloc_netdev: Too long device name\n");
>> +               return NULL;
>> +       }
> 
> Netdevice name isn't some random junk you get from userspace, so BUG is fine.

I agree, misuse of kernel APIs is not something we need to catch
verbosely.

Re: [PATCH v2] core: dev: don't call BUG() on bad input

[David Miller]

From: Vasiliy Kulikov <segoon@openwall.com>
Date: Mon, 14 Feb 2011 18:23:10 +0300

> On Mon, Feb 14, 2011 at 17:16 +0200, Alexey Dobriyan wrote:
>> Netdevice name isn't some random junk you get from userspace, so BUG is fine.
> 
> It IS for bluetooth, see net/bluetooth/bnep/core.c: bnep_add_connection() and
> net/bluetooth/bnep/sock.c: bnep_sock_ioctl(). 

If bluetooth wants to allow something so foolish, then it's bluetooth's
responsibility to sanity check the arguments before blinding passing
them into kernel APIs which expect sane inputs.

I'm not applying this.

Re: [PATCH v2] core: dev: don't call BUG() on bad input

[Tom Herbert]

On Mon, Feb 14, 2011 at 11:25 AM, David Miller <davem@davemloft.net> wrote:
> From: Vasiliy Kulikov <segoon@openwall.com>
> Date: Mon, 14 Feb 2011 18:23:10 +0300
>
>> On Mon, Feb 14, 2011 at 17:16 +0200, Alexey Dobriyan wrote:
>>> Netdevice name isn't some random junk you get from userspace, so BUG is fine.
>>
>> It IS for bluetooth, see net/bluetooth/bnep/core.c: bnep_add_connection() and
>> net/bluetooth/bnep/sock.c: bnep_sock_ioctl().
>
> If bluetooth wants to allow something so foolish, then it's bluetooth's
> responsibility to sanity check the arguments before blinding passing
> them into kernel APIs which expect sane inputs.
>
> I'm not applying this.
>

Changing to BUG_ON(txqs < 1) and BUG_ON(rxqs < 1) does make sense I think.

Tom

Re: [PATCH v2] core: dev: don't call BUG() on bad input

[David Miller]

From: Tom Herbert <therbert@google.com>
Date: Mon, 14 Feb 2011 11:33:29 -0800

> On Mon, Feb 14, 2011 at 11:25 AM, David Miller <davem@davemloft.net> wrote:
>> From: Vasiliy Kulikov <segoon@openwall.com>
>> Date: Mon, 14 Feb 2011 18:23:10 +0300
>>
>>> On Mon, Feb 14, 2011 at 17:16 +0200, Alexey Dobriyan wrote:
>>>> Netdevice name isn't some random junk you get from userspace, so BUG is fine.
>>>
>>> It IS for bluetooth, see net/bluetooth/bnep/core.c: bnep_add_connection() and
>>> net/bluetooth/bnep/sock.c: bnep_sock_ioctl().
>>
>> If bluetooth wants to allow something so foolish, then it's bluetooth's
>> responsibility to sanity check the arguments before blinding passing
>> them into kernel APIs which expect sane inputs.
>>
>> I'm not applying this.
>>
> 
> Changing to BUG_ON(txqs < 1) and BUG_ON(rxqs < 1) does make sense I think.

Sure.