From 07e7f7cc619d15645e45d04b1c99550c6d292e9c Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Tue, 11 May 2021 22:35:17 +0200 Subject: bpf: Add kconfig knob for disabling unpriv bpf by default commit 08389d888287c3823f80b0216766b71e17f0aba5 upstream. 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 Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/74ec548079189e4e4dffaeb42b8987bb3c852eee.1620765074.git.daniel@iogearbox.net [fllinden@amazon.com: backported to 4.19] Signed-off-by: Frank van der Linden Signed-off-by: Greg Kroah-Hartman --- Documentation/sysctl/kernel.txt | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) (limited to 'Documentation/sysctl') diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt index 37a679501ddc..8bd3b0153959 100644 --- a/Documentation/sysctl/kernel.txt +++ b/Documentation/sysctl/kernel.txt @@ -94,6 +94,7 @@ show up in /proc/sys/kernel: - sysctl_writes_strict - tainted - threads-max +- unprivileged_bpf_disabled - unknown_nmi_panic - watchdog - watchdog_thresh @@ -1041,6 +1042,26 @@ available RAM pages threads-max is reduced accordingly. ============================================================== +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 set to 1, this can't be cleared from the running kernel +anymore. + +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 + +============================================================== + unknown_nmi_panic: The value in this file affects behavior of handling NMI. When the -- cgit v1.2.3