Add KF_DESTRUCTIVE flag for destructive functions. Functions with this
flag set will require CAP_SYS_BOOT capabilities.
Signed-off-by: Artem Savkov <asavkov@xxxxxxxxxx>
---
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 c8b21de1c772..781731749e55 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 976cbdd2981f..ad93c2d9cc1c 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 28b02dc67a2a..2c1f8069f7b7 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 */
--
2.37.1
