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 <[email protected]>
Assisted-by: Codex:gpt-5.5
Signed-off-by: Tamir Duberstein <[email protected]>
---
tools/lib/bpf/ringbuf.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c
index 5737e02c1670..1c5bce2b5e12 100644
--- a/tools/lib/bpf/ringbuf.c
+++ b/tools/lib/bpf/ringbuf.c
@@ -274,7 +274,8 @@ 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) {
+ /* Positions wrap; the consumer cannot logically pass the
producer. */
+ while (cons_pos != prod_pos) {
len_ptr = r->data + (cons_pos & r->mask);
len = smp_load_acquire(len_ptr);
--
2.55.0.rc0.159.gbe5d7338c2
