Daniel Borkmann 8e2fe1d9f1 bpf: add new arg_type that allows for 0 sized stack buffer ... Currently, when we pass a buffer from the eBPF stack into a helper function, the function proto indicates argument types as ARG_PTR_TO_STACK and ARG_CONST_STACK_SIZE pair. If R<X> contains the former, then R<X+1> must be of the latter type. Then, verifier checks whether the buffer points into eBPF stack, is initialized, etc. The verifier also guarantees that the constant value passed in R<X+1> is greater than 0, so helper functions don't need to test for it and can always assume a non-NULL initialized buffer as well as non-0 buffer size. This patch adds a new argument types ARG_CONST_STACK_SIZE_OR_ZERO that allows to also pass NULL as R<X> and 0 as R<X+1> into the helper function. Such helper functions, of course, need to be able to handle these cases internally then. Verifier guarantees that either R<X> == NULL && R<X+1> == 0 or R<X> != NULL && R<X+1> != 0 (like the case of ARG_CONST_STACK_SIZE), any other combinations are not possible to load. I went through various options of extending the verifier, and introducing the type ARG_CONST_STACK_SIZE_OR_ZERO seems to have most minimal changes needed to the verifier. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>		2016-02-21 22:07:09 -05:00
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arraymap.c	bpf: add lookup/update support for per-cpu hash and array maps	2016-02-06 03:34:36 -05:00
core.c	bpf: move clearing of A/X into classic to eBPF migration prologue	2015-12-18 16:04:51 -05:00
hashtab.c	bpf: grab rcu read lock for bpf_percpu_hash_update	2016-02-19 14:37:43 -05:00
helpers.c	bpf: split state from prandom_u32() and consolidate {c, e}BPF prngs	2015-10-08 05:26:39 -07:00
inode.c	bpf, inode: allow for rename and link ops	2015-12-12 18:44:23 -05:00
Makefile	bpf: introduce BPF_MAP_TYPE_STACK_TRACE	2016-02-20 00:21:44 -05:00
stackmap.c	bpf: introduce BPF_MAP_TYPE_STACK_TRACE	2016-02-20 00:21:44 -05:00
syscall.c	bpf: add lookup/update support for per-cpu hash and array maps	2016-02-06 03:34:36 -05:00
verifier.c	bpf: add new arg_type that allows for 0 sized stack buffer	2016-02-21 22:07:09 -05:00