Description: | The cookie feature in the packet action API implementation in net/sched/act_api.c in the Linux kernel 4.11.x through 4.11-rc7 mishandles the tb nlattr array, which allows local users to cause a denial of service (uninitialized memory access and refcount underflow, and system hang or crash) or possibly have unspecified other impact via "tc filter add" commands in certain contexts. NOTE: this does not affect stable kernels, such as 4.10.x, from kernel.org. Fabian Grünbichler discovered that the Packet action API implementation in the Linux kernel improperly handled uninitialized data. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code.
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