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bpf: add destructive kfunc flag

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Add KF_DESTRUCTIVE flag for destructive functions. Functions with this
flag set will require CAP_SYS_BOOT capabilities.

Signed-off-by: Artem Savkov <asavkov@redhat.com>
Link: https://lore.kernel.org/r/20220810065905.475418-2-asavkov@redhat.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Artem Savkov 2022-08-10 08:59:03 +02:00 committed by Alexei Starovoitov
parent 3143d10b09
commit 4dd48c6f1f
3 changed files with 16 additions and 1 deletions
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9
Documentation/bpf/kfuncs.rst
View File

@ -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
--------------------------

3
include/linux/btf.h
View File

@ -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;

5
kernel/bpf/verifier.c
View File

@ -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 */