From: Dan Rosenberg <drosenberg@vsecurity.com>
To: Andrew Hendry <andrew.hendry@gmail.com>
Cc: netdev@vger.kernel.org, security@kernel.org, stable@kernel.org
Subject: Re: [SECURITY] memory corruption in X.25 facilities parsing
Date: Wed, 03 Nov 2010 19:44:31 -0400 [thread overview]
Message-ID: <1288827871.22123.0.camel@dan> (raw)
In-Reply-To: <1288824893.1858.5.camel@jaunty>
Looks good to me. Thanks for the quick turnaround.
-Dan
On Thu, 2010-11-04 at 09:54 +1100, Andrew Hendry wrote:
> On Wed, 2010-11-03 at 12:12 +1100, Andrew Hendry wrote:
> > There is an issue here, under select scenarios I can crash systems.
> > However the patch doesn't resolve it fully, I think after breaking at
> > that point the len and p pointers are messed up before it tries to
> > parse the next facility.
> >
> > Maybe it should return not break? It should reject/clear such calls.
> > I'll start checking if the callers properly handle errors.
> > Also should it be if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1),
> > because it does the memcpy with p[1] -1
> >
> >
> > On Wed, Nov 3, 2010 at 2:02 AM, Dan Rosenberg <drosenberg@vsecurity.com> wrote:
> > > I put this together after a quick glance, so if someone knows this code
> > > better than I do (i.e. at all), feel free to comment or drop this patch
> > > if it's unnecessary.
> > >
> > > A value of 0 will cause a memcpy() of ULONG_MAX size, destroying the
> > > kernel heap.
> > >
> > > Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>
> > >
> > > --- linux-2.6.36-rc6.orig/net/x25/x25_facilities.c 2010-09-28 21:01:22.000000000 -0400
> > > +++ linux-2.6.36-rc6/net/x25/x25_facilities.c 2010-11-02 10:36:02.827291324 -0400
> > > @@ -134,14 +134,14 @@ int x25_parse_facilities(struct sk_buff
> > > case X25_FAC_CLASS_D:
> > > switch (*p) {
> > > case X25_FAC_CALLING_AE:
> > > - if (p[1] > X25_MAX_DTE_FACIL_LEN)
> > > + if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] == 0)
> > > break;
> > > dte_facs->calling_len = p[2];
> > > memcpy(dte_facs->calling_ae, &p[3], p[1] - 1);
> > > *vc_fac_mask |= X25_MASK_CALLING_AE;
> > > break;
> > > case X25_FAC_CALLED_AE:
> > > - if (p[1] > X25_MAX_DTE_FACIL_LEN)
> > > + if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] == 0)
> > > break;
> > > dte_facs->called_len = p[2];
> > > memcpy(dte_facs->called_ae, &p[3], p[1] - 1);
> > >
> > >
> > >
>
> How does this look? It appears to fix it for the cases I could test.
>
> Signed-of-by: Andrew Hendry <andrew.hendry@gmail.com>
>
> diff --git a/net/x25/x25_facilities.c b/net/x25/x25_facilities.c
> index 771bab0..3a8c4c4 100644
> --- a/net/x25/x25_facilities.c
> +++ b/net/x25/x25_facilities.c
> @@ -134,15 +134,15 @@ int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities,
> case X25_FAC_CLASS_D:
> switch (*p) {
> case X25_FAC_CALLING_AE:
> - if (p[1] > X25_MAX_DTE_FACIL_LEN)
> - break;
> + if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1)
> + return 0;
> dte_facs->calling_len = p[2];
> memcpy(dte_facs->calling_ae, &p[3], p[1] - 1);
> *vc_fac_mask |= X25_MASK_CALLING_AE;
> break;
> case X25_FAC_CALLED_AE:
> - if (p[1] > X25_MAX_DTE_FACIL_LEN)
> - break;
> + if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1)
> + return 0;
> dte_facs->called_len = p[2];
> memcpy(dte_facs->called_ae, &p[3], p[1] - 1);
> *vc_fac_mask |= X25_MASK_CALLED_AE;
> diff --git a/net/x25/x25_in.c b/net/x25/x25_in.c
> index 6317896..1d80e10 100644
> --- a/net/x25/x25_in.c
> +++ b/net/x25/x25_in.c
> @@ -119,6 +119,8 @@ static int x25_state1_machine(struct sock *sk, struct sk_buff *skb, int frametyp
> &x25->vc_facil_mask);
> if (len > 0)
> skb_pull(skb, len);
> + else
> + return -1;
> /*
> * Copy any Call User Data.
> */
next prev parent reply other threads:[~2010-11-03 23:44 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-02 15:02 [SECURITY] memory corruption in X.25 facilities parsing Dan Rosenberg
2010-11-03 1:12 ` Andrew Hendry
2010-11-03 22:54 ` Andrew Hendry
2010-11-03 23:44 ` Dan Rosenberg [this message]
2010-11-04 1:56 ` David Miller
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