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* [PATCH bpf-next 00/11] RFC: Make check_func_arg table driven
@ 2020-09-04 11:23 Lorenz Bauer
  2020-09-04 11:23 ` [PATCH bpf-next 01/11] btf: Fix BTF_SET_START_GLOBAL macro Lorenz Bauer
                   ` (11 more replies)
  0 siblings, 12 replies; 28+ messages in thread
From: Lorenz Bauer @ 2020-09-04 11:23 UTC (permalink / raw)
  To: ast, yhs, daniel, kafai; +Cc: bpf, kernel-team, Lorenz Bauer

This is what happened when I got sidetracked from my work on sockmap
bpf_iter support [1]. For that I wanted to allow passing a BTF pointer
to functions expecting a PTR_TO_SOCKET. At first it wasn't at all
obvious to me how to add this to check_func_arg, so I started refactoring
the function bit by bit. This RFC series is the result of that.

Note: this series is based on top of sockmap iterator, hence the RFC status.

Currently, check_func_arg has this pretty gnarly if statement that
compares the valid arg_type with the actualy reg_type. Sprinkled
in-between are checks for register_is_null, to short circuit these
tests if we're dealing with a nullable arg_type. There is also some
code for later bounds / access checking hidden away in there.

This series of patches refactors the function into something like this:

   if (reg_is_null && arg_type_is_nullable)
     skip type checking

   do type checking, including BTF validation

   do bounds / access checking

The type checking is now table driven, which makes it easy to extend
the acceptable types. Maybe more importantly, using a table makes it
easy to provide more helpful verifier output (see the last patch).

I realise there are quite a few patches here. The most interesting
ones are #5 where I introduce a btf_id_set for each helper arg,
#10 where I simplify the nullable type checking and finally #11
where I add the table of compatible types.

There are some more simplifications that we could do that could get
rid of resolve_map_arg_type, but the series is already too long.

Martin: you said that you're working on extending PTR_TO_SOCK_COMMON,
would this series help you with that?

1: https://lore.kernel.org/bpf/20200904095904.612390-1-lmb@cloudflare.com/T/#t

Lorenz Bauer (11):
  btf: Fix BTF_SET_START_GLOBAL macro
  btf: add a global set of valid BTF socket ids
  btf: make btf_set_contains take a const pointer
  bpf: check scalar or invalid register in check_helper_mem_access
  bpf: allow specifying a set of BTF IDs for helper arguments
  bpf: make reference tracking in check_func_arg generic
  bpf: always check access to PTR_TO_CTX regardless of arg_type
  bpf: set meta->raw_mode for pointers to memory closer to it's use
  bpf: check ARG_PTR_TO_SPINLOCK register type in check_func_arg
  bpf: hoist type checking for nullable arg types
  bpf: use a table to drive helper arg type checks

 include/linux/bpf.h            |  25 ++-
 include/linux/btf_ids.h        |   7 +-
 kernel/bpf/bpf_inode_storage.c |   8 +-
 kernel/bpf/btf.c               |  24 +--
 kernel/bpf/stackmap.c          |   5 +-
 kernel/bpf/verifier.c          | 355 ++++++++++++++++++---------------
 kernel/trace/bpf_trace.c       |  15 +-
 net/core/bpf_sk_storage.c      |  10 +-
 net/core/filter.c              |  38 ++--
 net/ipv4/bpf_tcp_ca.c          |  24 +--
 tools/include/linux/btf_ids.h  |   7 +-
 11 files changed, 269 insertions(+), 249 deletions(-)

-- 
2.25.1


^ permalink raw reply	[flat|nested] 28+ messages in thread
end of thread, other threads:[~2020-09-09 10:15 UTC | newest]

Thread overview: 28+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-09-04 11:23 [PATCH bpf-next 00/11] RFC: Make check_func_arg table driven Lorenz Bauer
2020-09-04 11:23 ` [PATCH bpf-next 01/11] btf: Fix BTF_SET_START_GLOBAL macro Lorenz Bauer
2020-09-09  4:04   ` Andrii Nakryiko
2020-09-09  9:51     ` Lorenz Bauer
2020-09-04 11:23 ` [PATCH bpf-next 02/11] btf: add a global set of valid BTF socket ids Lorenz Bauer
2020-09-09  4:12   ` Andrii Nakryiko
2020-09-04 11:23 ` [PATCH bpf-next 03/11] btf: make btf_set_contains take a const pointer Lorenz Bauer
2020-09-09  4:13   ` Andrii Nakryiko
2020-09-04 11:23 ` [PATCH bpf-next 04/11] bpf: check scalar or invalid register in check_helper_mem_access Lorenz Bauer
2020-09-09  4:22   ` Andrii Nakryiko
2020-09-09 10:02     ` Lorenz Bauer
2020-09-04 11:23 ` [PATCH bpf-next 05/11] bpf: allow specifying a set of BTF IDs for helper arguments Lorenz Bauer
2020-09-06 23:04   ` Martin KaFai Lau
2020-09-07  9:15     ` Lorenz Bauer
2020-09-09  4:47   ` Andrii Nakryiko
2020-09-09  5:56     ` Martin KaFai Lau
2020-09-09 10:06       ` Lorenz Bauer
2020-09-09 10:11     ` Lorenz Bauer
2020-09-04 11:23 ` [PATCH bpf-next 06/11] bpf: make reference tracking in check_func_arg generic Lorenz Bauer
2020-09-09  4:50   ` Andrii Nakryiko
2020-09-04 11:23 ` [PATCH bpf-next 07/11] bpf: always check access to PTR_TO_CTX regardless of arg_type Lorenz Bauer
2020-09-04 11:23 ` [PATCH bpf-next 08/11] bpf: set meta->raw_mode for pointers to memory closer to it's use Lorenz Bauer
2020-09-04 11:23 ` [PATCH bpf-next 09/11] bpf: check ARG_PTR_TO_SPINLOCK register type in check_func_arg Lorenz Bauer
2020-09-04 11:24 ` [PATCH bpf-next 10/11] bpf: hoist type checking for nullable arg types Lorenz Bauer
2020-09-09  5:07   ` Andrii Nakryiko
2020-09-04 11:24 ` [PATCH bpf-next 11/11] bpf: use a table to drive helper arg type checks Lorenz Bauer
2020-09-09  6:17 ` [PATCH bpf-next 00/11] RFC: Make check_func_arg table driven Martin KaFai Lau
2020-09-09 10:15   ` Lorenz Bauer

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