On December 26, 2022 10:35:49 PM Stanislav Fomichev <stfomichev@xxxxxxxxx>
wrote:
On Fri, Dec 23, 2022 at 5:49 PM Stanislav Fomichev <sdf@xxxxxxxxxx> wrote:
get_func_ip() */
- tstamp_type_access:1; /* Accessed
__sk_buff->tstamp_type */
+ tstamp_type_access:1, /* Accessed
__sk_buff->tstamp_type */
+ valid_id:1; /* Is bpf_prog::aux::__id valid? */
enum bpf_prog_type type; /* Type of BPF program */
enum bpf_attach_type expected_attach_type; /* For some prog types */
u32 len; /* Number of filter blocks */
@@ -1688,6 +1689,12 @@ void bpf_prog_inc(struct bpf_prog *prog);
struct bpf_prog * __must_check bpf_prog_inc_not_zero(struct bpf_prog *prog);
void bpf_prog_put(struct bpf_prog *prog);
+static inline u32 bpf_prog_get_id(const struct bpf_prog *prog)
+{
+ if (WARN(!prog->valid_id, "Attempting to use an invalid eBPF program"))
+ return 0;
+ return prog->aux->__id;
+}
I'm still missing why we need to have this WARN and have a check at all.
IIUC, we're actually too eager in resetting the id to 0, and need to
keep that stale id around at least for perf/audit.
Why not have a flag only to protect against double-idr_remove
bpf_prog_free_id and keep the rest as is?
Which places are we concerned about that used to report id=0 but now
would report stale id?
What double-idr_remove are you concerned about?
bpf_prog_by_id() is doing bpf_prog_inc_not_zero
while __bpf_prog_put just dropped it to zero.
(traveling, sending from an untested setup, hope it reaches everyone)
There is a call to bpf_prog_free_id from __bpf_prog_offload_destroy which
tries to make offloaded program disappear from the idr when the netdev
goes offline. So I'm assuming that '!prog->aux->id' check in bpf_prog_free_id
is to handle that case where we do bpf_prog_free_id much earlier than the
rest of the __bpf_prog_put stuff.
Maybe just move bpf_prog_free_id() into bpf_prog_put_deferred()
after perf_event_bpf_event and bpf_audit_prog ?
Probably can remove the obsolete do_idr_lock bool flag as
separate patch?
+1 on removing do_idr_lock separately.
Much simpler fix and no code churn.
Both valid_id and saved_id approaches have flaws.
Given the __bpf_prog_offload_destroy path above, we still probably need
some flag to indicate that the id has been already removed from the idr?
So what do you guys want in a patch? Is there a consensus on what you
would merge to fix this bug/regression?
--
paul-moore.com
