Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

Alexei Starovoitov says:

====================
pull-request: bpf-next 2019-04-22

The following pull-request contains BPF updates for your *net-next* tree.

The main changes are:

1) allow stack/queue helpers from more bpf program types, from Alban.

2) allow parallel verification of root bpf programs, from Alexei.

3) introduce bpf sysctl hook for trusted root cases, from Andrey.

4) recognize var/datasec in btf deduplication, from Andrii.

5) cpumap performance optimizations, from Jesper.

6) verifier prep for alu32 optimization, from Jiong.

7) libbpf xsk cleanup, from Magnus.

8) other various fixes and cleanups.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

5 files changed, 165 insertions, 6 deletions

diff --git a/Documentation/bpf/bpf_design_QA.rst b/Documentation/bpf/bpf_design_QA.rst
index 10453c627135..cb402c59eca5 100644
--- a/Documentation/bpf/bpf_design_QA.rst
+++ b/Documentation/bpf/bpf_design_QA.rst
@@ -85,8 +85,33 @@ Q: Can loops be supported in a safe way?
 A: It's not clear yet.
 
 BPF developers are trying to find a way to
-support bounded loops where the verifier can guarantee that
-the program terminates in less than 4096 instructions.
+support bounded loops.
+
+Q: What are the verifier limits?
+--------------------------------
+A: The only limit known to the user space is BPF_MAXINSNS (4096).
+It's the maximum number of instructions that the unprivileged bpf
+program can have. The verifier has various internal limits.
+Like the maximum number of instructions that can be explored during
+program analysis. Currently, that limit is set to 1 million.
+Which essentially means that the largest program can consist
+of 1 million NOP instructions. There is a limit to the maximum number
+of subsequent branches, a limit to the number of nested bpf-to-bpf
+calls, a limit to the number of the verifier states per instruction,
+a limit to the number of maps used by the program.
+All these limits can be hit with a sufficiently complex program.
+There are also non-numerical limits that can cause the program
+to be rejected. The verifier used to recognize only pointer + constant
+expressions. Now it can recognize pointer + bounded_register.
+bpf_lookup_map_elem(key) had a requirement that 'key' must be
+a pointer to the stack. Now, 'key' can be a pointer to map value.
+The verifier is steadily getting 'smarter'. The limits are
+being removed. The only way to know that the program is going to
+be accepted by the verifier is to try to load it.
+The bpf development process guarantees that the future kernel
+versions will accept all bpf programs that were accepted by
+the earlier versions.
+
 
 Instruction level questions
 ---------------------------
diff --git a/Documentation/bpf/index.rst b/Documentation/bpf/index.rst
index 4e77932959cc..d3fe4cac0c90 100644
--- a/Documentation/bpf/index.rst
+++ b/Documentation/bpf/index.rst
@@ -36,6 +36,16 @@ Two sets of Questions and Answers (Q&A) are maintained.
    bpf_devel_QA
 
 
+Program types
+=============
+
+.. toctree::
+   :maxdepth: 1
+
+   prog_cgroup_sysctl
+   prog_flow_dissector
+
+
 .. Links:
 .. _Documentation/networking/filter.txt: ../networking/filter.txt
 .. _man-pages: https://www.kernel.org/doc/man-pages/
diff --git a/Documentation/bpf/prog_cgroup_sysctl.rst b/Documentation/bpf/prog_cgroup_sysctl.rst
new file mode 100644
index 000000000000..677d6c637cf3
--- /dev/null
+++ b/Documentation/bpf/prog_cgroup_sysctl.rst
@@ -0,0 +1,125 @@
+.. SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+
+===========================
+BPF_PROG_TYPE_CGROUP_SYSCTL
+===========================
+
+This document describes ``BPF_PROG_TYPE_CGROUP_SYSCTL`` program type that
+provides cgroup-bpf hook for sysctl.
+
+The hook has to be attached to a cgroup and will be called every time a
+process inside that cgroup tries to read from or write to sysctl knob in proc.
+
+1. Attach type
+**************
+
+``BPF_CGROUP_SYSCTL`` attach type has to be used to attach
+``BPF_PROG_TYPE_CGROUP_SYSCTL`` program to a cgroup.
+
+2. Context
+**********
+
+``BPF_PROG_TYPE_CGROUP_SYSCTL`` provides access to the following context from
+BPF program::
+
+    struct bpf_sysctl {
+        __u32 write;
+        __u32 file_pos;
+    };
+
+* ``write`` indicates whether sysctl value is being read (``0``) or written
+  (``1``). This field is read-only.
+
+* ``file_pos`` indicates file position sysctl is being accessed at, read
+  or written. This field is read-write. Writing to the field sets the starting
+  position in sysctl proc file ``read(2)`` will be reading from or ``write(2)``
+  will be writing to. Writing zero to the field can be used e.g. to override
+  whole sysctl value by ``bpf_sysctl_set_new_value()`` on ``write(2)`` even
+  when it's called by user space on ``file_pos > 0``. Writing non-zero
+  value to the field can be used to access part of sysctl value starting from
+  specified ``file_pos``. Not all sysctl support access with ``file_pos !=
+  0``, e.g. writes to numeric sysctl entries must always be at file position
+  ``0``. See also ``kernel.sysctl_writes_strict`` sysctl.
+
+See `linux/bpf.h`_ for more details on how context field can be accessed.
+
+3. Return code
+**************
+
+``BPF_PROG_TYPE_CGROUP_SYSCTL`` program must return one of the following
+return codes:
+
+* ``0`` means "reject access to sysctl";
+* ``1`` means "proceed with access".
+
+If program returns ``0`` user space will get ``-1`` from ``read(2)`` or
+``write(2)`` and ``errno`` will be set to ``EPERM``.
+
+4. Helpers
+**********
+
+Since sysctl knob is represented by a name and a value, sysctl specific BPF
+helpers focus on providing access to these properties:
+
+* ``bpf_sysctl_get_name()`` to get sysctl name as it is visible in
+  ``/proc/sys`` into provided by BPF program buffer;
+
+* ``bpf_sysctl_get_current_value()`` to get string value currently held by
+  sysctl into provided by BPF program buffer. This helper is available on both
+  ``read(2)`` from and ``write(2)`` to sysctl;
+
+* ``bpf_sysctl_get_new_value()`` to get new string value currently being
+  written to sysctl before actual write happens. This helper can be used only
+  on ``ctx->write == 1``;
+
+* ``bpf_sysctl_set_new_value()`` to override new string value currently being
+  written to sysctl before actual write happens. Sysctl value will be
+  overridden starting from the current ``ctx->file_pos``. If the whole value
+  has to be overridden BPF program can set ``file_pos`` to zero before calling
+  to the helper. This helper can be used only on ``ctx->write == 1``. New
+  string value set by the helper is treated and verified by kernel same way as
+  an equivalent string passed by user space.
+
+BPF program sees sysctl value same way as user space does in proc filesystem,
+i.e. as a string. Since many sysctl values represent an integer or a vector
+of integers, the following helpers can be used to get numeric value from the
+string:
+
+* ``bpf_strtol()`` to convert initial part of the string to long integer
+  similar to user space `strtol(3)`_;
+* ``bpf_strtoul()`` to convert initial part of the string to unsigned long
+  integer similar to user space `strtoul(3)`_;
+
+See `linux/bpf.h`_ for more details on helpers described here.
+
+5. Examples
+***********
+
+See `test_sysctl_prog.c`_ for an example of BPF program in C that access
+sysctl name and value, parses string value to get vector of integers and uses
+the result to make decision whether to allow or deny access to sysctl.
+
+6. Notes
+********
+
+``BPF_PROG_TYPE_CGROUP_SYSCTL`` is intended to be used in **trusted** root
+environment, for example to monitor sysctl usage or catch unreasonable values
+an application, running as root in a separate cgroup, is trying to set.
+
+Since `task_dfl_cgroup(current)` is called at `sys_read` / `sys_write` time it
+may return results different from that at `sys_open` time, i.e. process that
+opened sysctl file in proc filesystem may differ from process that is trying
+to read from / write to it and two such processes may run in different
+cgroups, what means ``BPF_PROG_TYPE_CGROUP_SYSCTL`` should not be used as a
+security mechanism to limit sysctl usage.
+
+As with any cgroup-bpf program additional care should be taken if an
+application running as root in a cgroup should not be allowed to
+detach/replace BPF program attached by administrator.
+
+.. Links
+.. _linux/bpf.h: ../../include/uapi/linux/bpf.h
+.. _strtol(3): http://man7.org/linux/man-pages/man3/strtol.3p.html
+.. _strtoul(3): http://man7.org/linux/man-pages/man3/strtoul.3p.html
+.. _test_sysctl_prog.c:
+   ../../tools/testing/selftests/bpf/progs/test_sysctl_prog.c
diff --git a/Documentation/networking/bpf_flow_dissector.rst b/Documentation/bpf/prog_flow_dissector.rst
index b375ae2ec2c4..ed343abe541e 100644
--- a/Documentation/networking/bpf_flow_dissector.rst
+++ b/Documentation/bpf/prog_flow_dissector.rst
@@ -1,8 +1,8 @@
 .. SPDX-License-Identifier: GPL-2.0
 
-==================
-BPF Flow Dissector
-==================
+============================
+BPF_PROG_TYPE_FLOW_DISSECTOR
+============================
 
 Overview
 ========
diff --git a/Documentation/networking/index.rst b/Documentation/networking/index.rst
index 269d6f2661d5..f390fe3cfdfb 100644
--- a/Documentation/networking/index.rst
+++ b/Documentation/networking/index.rst
@@ -9,7 +9,6 @@ Contents:
    netdev-FAQ
    af_xdp
    batman-adv
-   bpf_flow_dissector
    can
    can_ucan_protocol
    device_drivers/freescale/dpaa2/index