From: Brendan Jackman jackmanb@google.com
[ Upstream commit 2a30f9440640c418bcfbea9b2b344d268b58e0a2 ]
One of our benchmarks running in (Google-internal) CI pushes data through the ringbuf faster htan than userspace is able to consume it. In this case it seems we're actually able to get >INT_MAX entries in a single ring_buffer__consume() call. ASAN detected that cnt overflows in this case.
Fix by using 64-bit counter internally and then capping the result to INT_MAX before converting to the int return type. Do the same for the ring_buffer__poll().
Fixes: bf99c936f947 (libbpf: Add BPF ring buffer support) Signed-off-by: Brendan Jackman jackmanb@google.com Signed-off-by: Andrii Nakryiko andrii@kernel.org Link: https://lore.kernel.org/bpf/20210429130510.1621665-1-jackmanb@google.com Signed-off-by: Sasha Levin sashal@kernel.org --- tools/lib/bpf/ringbuf.c | 30 +++++++++++++++++++++--------- 1 file changed, 21 insertions(+), 9 deletions(-)
diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c index 06cd709a3453..86c31c787fb9 100644 --- a/tools/lib/bpf/ringbuf.c +++ b/tools/lib/bpf/ringbuf.c @@ -202,9 +202,11 @@ static inline int roundup_len(__u32 len) return (len + 7) / 8 * 8; }
-static int ringbuf_process_ring(struct ring* r) +static int64_t ringbuf_process_ring(struct ring* r) { - int *len_ptr, len, err, cnt = 0; + int *len_ptr, len, err; + /* 64-bit to avoid overflow in case of extreme application behavior */ + int64_t cnt = 0; unsigned long cons_pos, prod_pos; bool got_new_data; void *sample; @@ -244,12 +246,14 @@ done: }
/* Consume available ring buffer(s) data without event polling. - * Returns number of records consumed across all registered ring buffers, or - * negative number if any of the callbacks return error. + * Returns number of records consumed across all registered ring buffers (or + * INT_MAX, whichever is less), or negative number if any of the callbacks + * return error. */ int ring_buffer__consume(struct ring_buffer *rb) { - int i, err, res = 0; + int64_t err, res = 0; + int i;
for (i = 0; i < rb->ring_cnt; i++) { struct ring *ring = &rb->rings[i]; @@ -259,18 +263,24 @@ int ring_buffer__consume(struct ring_buffer *rb) return err; res += err; } + if (res > INT_MAX) + return INT_MAX; return res; }
/* Poll for available data and consume records, if any are available. - * Returns number of records consumed, or negative number, if any of the - * registered callbacks returned error. + * Returns number of records consumed (or INT_MAX, whichever is less), or + * negative number, if any of the registered callbacks returned error. */ int ring_buffer__poll(struct ring_buffer *rb, int timeout_ms) { - int i, cnt, err, res = 0; + int i, cnt; + int64_t err, res = 0;
cnt = epoll_wait(rb->epoll_fd, rb->events, rb->ring_cnt, timeout_ms); + if (cnt < 0) + return -errno; + for (i = 0; i < cnt; i++) { __u32 ring_id = rb->events[i].data.fd; struct ring *ring = &rb->rings[ring_id]; @@ -280,5 +290,7 @@ int ring_buffer__poll(struct ring_buffer *rb, int timeout_ms) return err; res += err; } - return cnt < 0 ? -errno : res; + if (res > INT_MAX) + return INT_MAX; + return res; }