[PATCH bpf 3/6] libbpf: ringbuf: Handle position counter wrap

[Tamir Duberstein <tamird@kernel.org>]

Ring buffer positions are unsigned long counters and can wrap on 32-bit
systems. ringbuf_process_ring() stops consuming when producer_pos wraps
below consumer_pos because it compares the counters by magnitude.

Compare the positions for equality instead. The producer cannot move
logically behind the consumer in a non-overwrite ring.

Fixes: bf99c936f947 ("libbpf: Add BPF ring buffer support")
Reported-by: Andrew Werner <awerner32@gmail.com>
Assisted-by: Codex:gpt-5.5
Signed-off-by: Tamir Duberstein <tamird@kernel.org>
---
 tools/lib/bpf/ringbuf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c
index ae7fa79b6217..b7adce37b519 100644
--- a/tools/lib/bpf/ringbuf.c
+++ b/tools/lib/bpf/ringbuf.c
@@ -268,7 +268,7 @@ static int64_t ringbuf_process_ring(struct ring *r, size_t n)
 	do {
 		got_new_data = false;
 		prod_pos = smp_load_acquire(r->producer_pos);
-		while (cons_pos < prod_pos) {
+		while (cons_pos != prod_pos) {
 			len_ptr = r->data + (cons_pos & r->mask);
 			len = smp_load_acquire(len_ptr);
 

-- 
2.55.0.rc0.96.gc050c23164