I do not see any unfixable issues.
Kostja, please make a high-level overview before i send a detailed path 
review.

On Thursday, March 29, 2018 10:36:58 AM MSK Ilya Markov wrote:
> branch: gh-3250-system-space-access
> 
> Ilya Markov (2):
>   box: Add system view for _sequence system space
>   security: Refactor reads from systems spaces
> 
> imarkov (1):
>   security: Refactor system space access checks
> 
>  src/box/alter.cc                   | 283
> +++++++++++++++++++++++-------------- src/box/bootstrap.snap             |
> Bin 1504 -> 1540 bytes
>  src/box/index.cc                   |   1 +
>  src/box/lua/schema.lua             | 123 +++++++++-------
>  src/box/lua/space.cc               |   2 +
>  src/box/lua/upgrade.lua            |  34 +++--
>  src/box/schema.cc                  | 119 +++++++++++++++-
>  src/box/schema.h                   |  28 +++-
>  src/box/schema_def.h               |   2 +
>  src/box/space.c                    |   3 +-
>  src/box/space.h                    |  17 ++-
>  src/box/sysview_engine.c           |   4 +
>  src/box/sysview_index.c            |  80 ++++++++---
>  src/box/user.cc                    |   4 -
>  src/box/user.h                     |   7 +
>  test/app-tap/tarantoolctl.test.lua |   4 +-
>  test/box-py/bootstrap.result       |  11 +-
>  test/box/access.result             |  95 ++++++++-----
>  test/box/access.test.lua           |  48 ++++---
>  test/box/access_bin.result         |   8 +-
>  test/box/access_misc.result        |  51 +++++--
>  test/box/access_misc.test.lua      |  11 +-
>  test/box/access_sysview.result     |  88 ++++++++++--
>  test/box/access_sysview.test.lua   |  34 ++++-
>  test/box/alter.result              |   3 +
>  test/box/net.box.result            |   6 +
>  test/box/net.box.test.lua          |   2 +
>  test/box/on_replace.result         |  12 +-
>  test/box/role.result               |  27 +++-
>  test/box/role.test.lua             |  13 +-
>  test/box/sequence.result           |  17 ++-
>  test/box/sequence.test.lua         |  10 +-
>  test/box/transaction.result        |   8 +-
>  test/engine/iterator.result        |   2 +-
>  test/engine/savepoint.result       |  12 +-
>  test/engine/truncate.result        |   2 +-
>  test/xlog/upgrade.result           |  11 +-
>  37 files changed, 843 insertions(+), 339 deletions(-)