linux-kernel - [PATCH 5.11 051/210] libbpf: Fix bail out from ringbuf_process

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Message-Id: <20210412084017.705893143@linuxfoundation.org>
Date:   Mon, 12 Apr 2021 10:39:16 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Pedro Tammela <pctammela@...atatu.com>,
        Andrii Nakryiko <andrii@...nel.org>
Subject: [PATCH 5.11 051/210] libbpf: Fix bail out from ringbuf_process_ring() on error

From: Pedro Tammela <pctammela@...il.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@...atatu.com>
Signed-off-by: Andrii Nakryiko <andrii@...nel.org>
Link: https://lore.kernel.org/bpf/20210325150115.138750-1-pctammela@mojatatu.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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);