* [PATCH bpf 1/2] bpf, kconfig: Add consolidated menu entry for bpf with core options
@ 2021-05-11 20:35 Daniel Borkmann
2021-05-11 20:35 ` [PATCH bpf 2/2] bpf: Add kconfig knob for disabling unpriv bpf by default Daniel Borkmann
0 siblings, 1 reply; 2+ messages in thread
From: Daniel Borkmann @ 2021-05-11 20:35 UTC (permalink / raw)
To: alexei.starovoitov; +Cc: andrii, bpf, netdev, Daniel Borkmann
Right now, all core BPF related options are scattered in different Kconfig
locations mainly due to historic reasons. Moving forward, lets add a proper
subsystem entry under ...
General setup --->
BPF subsystem --->
... in order to have all knobs in a single location and thus ease BPF related
configuration. Networking related bits such as sockmap are out of scope for
the general setup and therefore better suited to remain in net/Kconfig.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
init/Kconfig | 41 +-----------------------
kernel/bpf/Kconfig | 78 ++++++++++++++++++++++++++++++++++++++++++++++
net/Kconfig | 27 ----------------
3 files changed, 79 insertions(+), 67 deletions(-)
create mode 100644 kernel/bpf/Kconfig
diff --git a/init/Kconfig b/init/Kconfig
index ca559ccdaa32..2282a6842dc6 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -439,6 +439,7 @@ config AUDITSYSCALL
source "kernel/irq/Kconfig"
source "kernel/time/Kconfig"
+source "kernel/bpf/Kconfig"
source "kernel/Kconfig.preempt"
menu "CPU/Task time and stats accounting"
@@ -1705,46 +1706,6 @@ config KALLSYMS_BASE_RELATIVE
# syscall, maps, verifier
-config BPF_LSM
- bool "LSM Instrumentation with BPF"
- depends on BPF_EVENTS
- depends on BPF_SYSCALL
- depends on SECURITY
- depends on BPF_JIT
- help
- Enables instrumentation of the security hooks with eBPF programs for
- implementing dynamic MAC and Audit Policies.
-
- If you are unsure how to answer this question, answer N.
-
-config BPF_SYSCALL
- bool "Enable bpf() system call"
- select BPF
- select IRQ_WORK
- select TASKS_TRACE_RCU
- select BINARY_PRINTF
- select NET_SOCK_MSG if INET
- default n
- help
- Enable the bpf() system call that allows to manipulate eBPF
- programs and maps via file descriptors.
-
-config ARCH_WANT_DEFAULT_BPF_JIT
- bool
-
-config BPF_JIT_ALWAYS_ON
- bool "Permanently enable BPF JIT and remove BPF interpreter"
- depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
- help
- Enables BPF JIT and removes BPF interpreter to avoid
- speculative execution of BPF instructions by the interpreter
-
-config BPF_JIT_DEFAULT_ON
- def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON
- depends on HAVE_EBPF_JIT && BPF_JIT
-
-source "kernel/bpf/preload/Kconfig"
-
config USERFAULTFD
bool "Enable userfaultfd() system call"
depends on MMU
diff --git a/kernel/bpf/Kconfig b/kernel/bpf/Kconfig
new file mode 100644
index 000000000000..b4edaefc6255
--- /dev/null
+++ b/kernel/bpf/Kconfig
@@ -0,0 +1,78 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+# BPF interpreter that, for example, classic socket filters depend on.
+config BPF
+ bool
+
+# Used by archs to tell that they support BPF JIT compiler plus which
+# flavour. Only one of the two can be selected for a specific arch since
+# eBPF JIT supersedes the cBPF JIT.
+
+# Classic BPF JIT (cBPF)
+config HAVE_CBPF_JIT
+ bool
+
+# Extended BPF JIT (eBPF)
+config HAVE_EBPF_JIT
+ bool
+
+# Used by archs to tell that they want the BPF JIT compiler enabled by
+# default for kernels that were compiled with BPF JIT support.
+config ARCH_WANT_DEFAULT_BPF_JIT
+ bool
+
+menu "BPF subsystem"
+
+config BPF_SYSCALL
+ bool "Enable bpf() system call"
+ select BPF
+ select IRQ_WORK
+ select TASKS_TRACE_RCU
+ select BINARY_PRINTF
+ select NET_SOCK_MSG if INET
+ default n
+ help
+ Enable the bpf() system call that allows to manipulate BPF programs
+ and maps via file descriptors.
+
+config BPF_JIT
+ bool "Enable BPF Just In Time compiler"
+ depends on HAVE_CBPF_JIT || HAVE_EBPF_JIT
+ depends on MODULES
+ help
+ BPF programs are normally handled by a BPF interpreter. This option
+ allows the kernel to generate native code when a program is loaded
+ into the kernel. This will significantly speed-up processing of BPF
+ programs.
+
+ Note, an admin should enable this feature changing:
+ /proc/sys/net/core/bpf_jit_enable
+ /proc/sys/net/core/bpf_jit_harden (optional)
+ /proc/sys/net/core/bpf_jit_kallsyms (optional)
+
+config BPF_JIT_ALWAYS_ON
+ bool "Permanently enable BPF JIT and remove BPF interpreter"
+ depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
+ help
+ Enables BPF JIT and removes BPF interpreter to avoid speculative
+ execution of BPF instructions by the interpreter.
+
+config BPF_JIT_DEFAULT_ON
+ def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON
+ depends on HAVE_EBPF_JIT && BPF_JIT
+
+source "kernel/bpf/preload/Kconfig"
+
+config BPF_LSM
+ bool "Enable BPF LSM Instrumentation"
+ depends on BPF_EVENTS
+ depends on BPF_SYSCALL
+ depends on SECURITY
+ depends on BPF_JIT
+ help
+ Enables instrumentation of the security hooks with BPF programs for
+ implementing dynamic MAC and Audit Policies.
+
+ If you are unsure how to answer this question, answer N.
+
+endmenu # "BPF subsystem"
diff --git a/net/Kconfig b/net/Kconfig
index f5ee7c65e6b4..c7392c449b25 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -302,21 +302,6 @@ config BQL
select DQL
default y
-config BPF_JIT
- bool "enable BPF Just In Time compiler"
- depends on HAVE_CBPF_JIT || HAVE_EBPF_JIT
- depends on MODULES
- help
- Berkeley Packet Filter filtering capabilities are normally handled
- by an interpreter. This option allows kernel to generate a native
- code when filter is loaded in memory. This should speedup
- packet sniffing (libpcap/tcpdump).
-
- Note, admin should enable this feature changing:
- /proc/sys/net/core/bpf_jit_enable
- /proc/sys/net/core/bpf_jit_harden (optional)
- /proc/sys/net/core/bpf_jit_kallsyms (optional)
-
config BPF_STREAM_PARSER
bool "enable BPF STREAM_PARSER"
depends on INET
@@ -470,15 +455,3 @@ config ETHTOOL_NETLINK
e.g. notification messages.
endif # if NET
-
-# Used by archs to tell that they support BPF JIT compiler plus which flavour.
-# Only one of the two can be selected for a specific arch since eBPF JIT supersedes
-# the cBPF JIT.
-
-# Classic BPF JIT (cBPF)
-config HAVE_CBPF_JIT
- bool
-
-# Extended BPF JIT (eBPF)
-config HAVE_EBPF_JIT
- bool
--
2.21.0
^ permalink raw reply related [flat|nested] 2+ messages in thread* [PATCH bpf 2/2] bpf: Add kconfig knob for disabling unpriv bpf by default 2021-05-11 20:35 [PATCH bpf 1/2] bpf, kconfig: Add consolidated menu entry for bpf with core options Daniel Borkmann @ 2021-05-11 20:35 ` Daniel Borkmann 0 siblings, 0 replies; 2+ messages in thread From: Daniel Borkmann @ 2021-05-11 20:35 UTC (permalink / raw) To: alexei.starovoitov; +Cc: andrii, bpf, netdev, Daniel Borkmann Add a kconfig knob which allows for unprivileged bpf to be disabled by default. If set, the knob sets /proc/sys/kernel/unprivileged_bpf_disabled to value of 2. This still allows a transition of 2 -> {0,1} through an admin. Similarly, this also still keeps 1 -> {1} behavior intact, so that once set to permanently disabled, it cannot be undone aside from a reboot. We've also added extra2 with max of 2 for the procfs handler, so that an admin still has a chance to toggle between 0 <-> 2. Either way, as an additional alternative, applications can make use of CAP_BPF that we added a while ago. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> --- Documentation/admin-guide/sysctl/kernel.rst | 17 +++++++++--- kernel/bpf/Kconfig | 10 +++++++ kernel/bpf/syscall.c | 3 ++- kernel/sysctl.c | 29 +++++++++++++++++---- 4 files changed, 50 insertions(+), 9 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 ======== diff --git a/kernel/bpf/Kconfig b/kernel/bpf/Kconfig index b4edaefc6255..26b591e23f16 100644 --- a/kernel/bpf/Kconfig +++ b/kernel/bpf/Kconfig @@ -61,6 +61,16 @@ config BPF_JIT_DEFAULT_ON def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON depends on HAVE_EBPF_JIT && BPF_JIT +config BPF_UNPRIV_DEFAULT_OFF + bool "Disable unprivileged BPF by default" + depends on BPF_SYSCALL + help + Disables unprivileged BPF by default by setting the corresponding + /proc/sys/kernel/unprivileged_bpf_disabled knob to 2. An admin can + still reenable it by setting it to 0 later on, or permanently + disable it by setting it to 1 (from which no other transition to + 0 is possible anymore). + source "kernel/bpf/preload/Kconfig" config BPF_LSM diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 941ca06d9dfa..ea04b0deb5ce 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -50,7 +50,8 @@ static DEFINE_SPINLOCK(map_idr_lock); static DEFINE_IDR(link_idr); static DEFINE_SPINLOCK(link_idr_lock); -int sysctl_unprivileged_bpf_disabled __read_mostly; +int sysctl_unprivileged_bpf_disabled __read_mostly = + IS_BUILTIN(CONFIG_BPF_UNPRIV_DEFAULT_OFF) ? 2 : 0; static const struct bpf_map_ops * const bpf_map_types[] = { #define BPF_PROG_TYPE(_id, _name, prog_ctx_type, kern_ctx_type) diff --git a/kernel/sysctl.c b/kernel/sysctl.c index f91d327273c1..6df7c81f7cdd 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -225,7 +225,27 @@ static int bpf_stats_handler(struct ctl_table *table, int write, mutex_unlock(&bpf_stats_enabled_mutex); return ret; } -#endif + +static int bpf_unpriv_handler(struct ctl_table *table, int write, + void *buffer, size_t *lenp, loff_t *ppos) +{ + int ret, unpriv_enable = *(int *)table->data; + bool locked_state = unpriv_enable == 1; + struct ctl_table tmp = *table; + + if (write && !capable(CAP_SYS_ADMIN)) + return -EPERM; + + tmp.data = &unpriv_enable; + ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos); + if (write && !ret) { + if (locked_state && unpriv_enable != 1) + return -EPERM; + *(int *)table->data = unpriv_enable; + } + return ret; +} +#endif /* CONFIG_BPF_SYSCALL && CONFIG_SYSCTL */ /* * /proc/sys support @@ -2600,10 +2620,9 @@ static struct ctl_table kern_table[] = { .data = &sysctl_unprivileged_bpf_disabled, .maxlen = sizeof(sysctl_unprivileged_bpf_disabled), .mode = 0644, - /* only handle a transition from default "0" to "1" */ - .proc_handler = proc_dointvec_minmax, - .extra1 = SYSCTL_ONE, - .extra2 = SYSCTL_ONE, + .proc_handler = bpf_unpriv_handler, + .extra1 = SYSCTL_ZERO, + .extra2 = &two, }, { .procname = "bpf_stats_enabled", -- 2.21.0 ^ permalink raw reply related [flat|nested] 2+ messages in thread
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