libbpf: Fix bail out from 'ringbuf_process_ring()' on error

BugLink: https://bugs.launchpad.net/bugs/1926368
commit 6032ebb54c60cae24329f6aba3ce0c1ca8ad6abe upstream.

The current code bails out with negative and positive returns.
If the callback returns a positive return code, 'ring_buffer__consume()'
and 'ring_buffer__poll()' will return a spurious number of records
consumed, but mostly important will continue the processing loop.

This patch makes positive returns from the callback a no-op.

Fixes: bf99c936f947 ("libbpf: Add BPF ring buffer support")
Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210325150115.138750-1-pctammela@mojatatu.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c
index 8caaafe7e312b30eed538e39c2324f4065895754..e7a8d847161f28e265b0a400c5f35e5e67c60b93 100644 (file)
--- a/tools/lib/bpf/ringbuf.c
+++ b/tools/lib/bpf/ringbuf.c
@@ -227,7 +227,7 @@ static int ringbuf_process_ring(struct ring* r)
                        if ((len & BPF_RINGBUF_DISCARD_BIT) == 0) {
                                sample = (void *)len_ptr + BPF_RINGBUF_HDR_SZ;
                                err = r->sample_cb(r->ctx, sample, len);
-                               if (err) {
+                               if (err < 0) {
                                        /* update consumer pos and bail out */
                                        smp_store_release(r->consumer_pos,
                                                          cons_pos);