Re: BUG: unable to handle kernel NULL pointer dereference in ipv6_select_ident

Steffen Klassert
2011-12-22T06:38:14Z

On Thu, Dec 22, 2011 at 05:37:36AM +0100, Eric Dumazet wrote:
> Le mercredi 21 décembre 2011 à 23:12 +0000, Chris Boot a écrit :
> >
> > (gdb) list *ip_fragment+0x9d
> > 0xffffffff812a62e1 is in ip_fragment (include/net/dst.h:209).
> > 204 return dst_metric(dst, RTAX_FEATURES) & feature;
> > 205 }
> > 206
> > 207 static inline u32 dst_mtu(const struct dst_entry *dst)
> > 208 {
> > 209 return dst->ops->mtu(dst);
> > 210 }
> > 211
> > 212 /* RTT metrics are stored in milliseconds for user ABI, but used as jiffies */
>
> This one is different, its not IPv6 related but IPv4 :
>
> fake_dst_ops lacks a .mtu() field
>
> Bug added in commit 618f9bc74a039da76 (net: Move mtu handling down to
> the protocol depended handlers)
>

Before I did this patch, I changed the .default_mtu field of "struct dst_ops"
to .mtu and converted all users of default_mtu to mtu. fake_dst_ops never
had a default_mtu field, so I did not touch it. I guess this bug is arround
since fake_dst_ops exists. It's now just much easier to trigger as commit
618f9bc74a039da76 changed dst_mtu() to call dst->ops->mtu() unconditionally.