From 4dd48c6f1f83290d4bc61b43e61d86f8bc6c310e Mon Sep 17 00:00:00 2001 From: Artem Savkov Date: Wed, 10 Aug 2022 08:59:03 +0200 Subject: [PATCH] bpf: add destructive kfunc flag Add KF_DESTRUCTIVE flag for destructive functions. Functions with this flag set will require CAP_SYS_BOOT capabilities. Signed-off-by: Artem Savkov Link: https://lore.kernel.org/r/20220810065905.475418-2-asavkov@redhat.com Signed-off-by: Alexei Starovoitov --- Documentation/bpf/kfuncs.rst | 9 +++++++++ include/linux/btf.h | 3 ++- kernel/bpf/verifier.c | 5 +++++ 3 files changed, 16 insertions(+), 1 deletion(-) diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst index c8b21de..78173174 100644 --- a/Documentation/bpf/kfuncs.rst +++ b/Documentation/bpf/kfuncs.rst @@ -152,6 +152,15 @@ ensure the integrity of the operation being performed on the expected object. The KF_SLEEPABLE flag is used for kfuncs that may sleep. Such kfuncs can only be called by sleepable BPF programs (BPF_F_SLEEPABLE). +2.4.7 KF_DESTRUCTIVE flag +-------------------------- + +The KF_DESTRUCTIVE flag is used to indicate functions calling which is +destructive to the system. For example such a call can result in system +rebooting or panicking. Due to this additional restrictions apply to these +calls. At the moment they only require CAP_SYS_BOOT capability, but more can be +added later. + 2.5 Registering the kfuncs -------------------------- diff --git a/include/linux/btf.h b/include/linux/btf.h index 976cbdd..ad93c2d 100644 --- a/include/linux/btf.h +++ b/include/linux/btf.h @@ -49,7 +49,8 @@ * for this case. */ #define KF_TRUSTED_ARGS (1 << 4) /* kfunc only takes trusted pointer arguments */ -#define KF_SLEEPABLE (1 << 5) /* kfunc may sleep */ +#define KF_SLEEPABLE (1 << 5) /* kfunc may sleep */ +#define KF_DESTRUCTIVE (1 << 6) /* kfunc performs destructive actions */ struct btf; struct btf_member; diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 28b02dc..2c1f806 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -7584,6 +7584,11 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, func_name); return -EACCES; } + if (*kfunc_flags & KF_DESTRUCTIVE && !capable(CAP_SYS_BOOT)) { + verbose(env, "destructive kfunc calls require CAP_SYS_BOOT capabilities\n"); + return -EACCES; + } + acq = *kfunc_flags & KF_ACQUIRE; /* Check the arguments */ -- 2.7.4