The ptrace call in the Linux kernel 2.6.8.1 and 2.6.10 for the AMD64 platform allows local users to cause a denial of service (kernel crash) via a "non-canonical" address.
Exploitability
AV:LAC:LAu:NImpact
C:NI:NA:P2.1/AV:L/AC:L/Au:N/C:N/I:N/A:P