From: Daniel Borkmann <daniel@...> Date: Tue, 08 Aug 2017 02:46:16 +0200
On 08/07/2017 04:21 PM, Edward Cree wrote:
This series simplifies alignment tracking, generalises bounds tracking and fixes some bounds-tracking bugs in the BPF verifier. Pointer arithmetic on packet pointers, stack pointers, map value pointers and context pointers has been unified, and bounds on these pointers are only checked when the pointer is dereferenced. Operations on pointers which destroy all relation to the original pointer (such as multiplies and shifts) are disallowed if !env->allow_ptr_leaks, otherwise they convert the pointer to an unknown scalar and feed it to the normal scalar arithmetic handling. Pointer types have been unified with the corresponding adjusted-pointer types where those existed (e.g. PTR_TO_MAP_VALUE[_ADJ] or FRAME_PTR vs PTR_TO_STACK); similarly, CONST_IMM and UNKNOWN_VALUE have been unified into SCALAR_VALUE. Pointer types (except CONST_PTR_TO_MAP, PTR_TO_MAP_VALUE_OR_NULL and PTR_TO_PACKET_END, which do not allow arithmetic) have a 'fixed offset' and a 'variable offset'; the former is used when e.g. adding an immediate or a known-constant register, as long as it does not overflow. Otherwise the latter is used, and any operation creating a new variable offset creates a new 'id' (and, for PTR_TO_PACKET, clears the 'range'). SCALAR_VALUEs use the 'variable offset' fields to track the range of possible values; the 'fixed offset' should never be set on a scalar.
Been testing and reviewing the series over the last several days, looks reasonable to me as far as I can tell. Thanks for all the hard work on unifying this, Edward!
