[PATCH 5.11 051/210] libbpf: Fix bail out from ringbuf_process_ring() on error

Greg Kroah-Hartman
2021-04-12T09:31:03Z

From: Pedro Tammela <pctammela@gmail.com>

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>
---
tools/lib/bpf/ringbuf.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/tools/lib/bpf/ringbuf.c
+++ b/tools/lib/bpf/ringbuf.c
@@ -227,7 +227,7 @@ static int ringbuf_process_ring(struct 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);