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

Daniel Borkmann says:

====================
pull-request: bpf 2021-05-11

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

We've added 13 non-merge commits during the last 8 day(s) which contain
a total of 21 files changed, 817 insertions(+), 382 deletions(-).

The main changes are:

1) Fix multiple ringbuf bugs in particular to prevent writable mmap of
   read-only pages, from Andrii Nakryiko & Thadeu Lima de Souza Cascardo.

2) Fix verifier alu32 known-const subregister bound tracking for bitwise
   operations and/or/xor, from Daniel Borkmann.

3) Reject trampoline attachment for functions with variable arguments,
   and also add a deny list of other forbidden functions, from Jiri Olsa.

4) Fix nested bpf_bprintf_prepare() calls used by various helpers by
   switching to per-CPU buffers, from Florent Revest.

5) Fix kernel compilation with BTF debug info on ppc64 due to pahole
   missing TCP-CC functions like cubictcp_init, from Martin KaFai Lau.

6) Add a kconfig entry to provide an option to disallow unprivileged
   BPF by default, from Daniel Borkmann.

7) Fix libbpf compilation for older libelf when GELF_ST_VISIBILITY()
   macro is not available, from Arnaldo Carvalho de Melo.

8) Migrate test_tc_redirect to test_progs framework as prep work
   for upcoming skb_change_head() fix & selftest, from Jussi Maki.

9) Fix a libbpf segfault in add_dummy_ksym_var() if BTF is not
   present, from Ian Rogers.

10) Fix tx_only micro-benchmark in xdpsock BPF sample with proper frame
    size, from Magnus Karlsson.
====================

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

1 files changed, 14 insertions, 3 deletions

diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index 1d56a6b73a4e..24ab20d7a50a 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -1457,11 +1457,22 @@ unprivileged_bpf_disabled
 =========================
 
 Writing 1 to this entry will disable unprivileged calls to ``bpf()``;
-once disabled, calling ``bpf()`` without ``CAP_SYS_ADMIN`` will return
-``-EPERM``.
+once disabled, calling ``bpf()`` without ``CAP_SYS_ADMIN`` or ``CAP_BPF``
+will return ``-EPERM``. Once set to 1, this can't be cleared from the
+running kernel anymore.
 
-Once set, this can't be cleared.
+Writing 2 to this entry will also disable unprivileged calls to ``bpf()``,
+however, an admin can still change this setting later on, if needed, by
+writing 0 or 1 to this entry.
 
+If ``BPF_UNPRIV_DEFAULT_OFF`` is enabled in the kernel config, then this
+entry will default to 2 instead of 0.
+
+= =============================================================
+0 Unprivileged calls to ``bpf()`` are enabled
+1 Unprivileged calls to ``bpf()`` are disabled without recovery
+2 Unprivileged calls to ``bpf()`` are disabled
+= =============================================================
 
 watchdog
 ========