ring_buffer__new() and ring_buffer__add() allow a NULL sample callback. When callback-based consumption reaches such a ring, it calls through the NULL function pointer and crashes. Check every ring before manager polling or consumption so a missing callback returns -EINVAL before the manager waits or consumes another ring. Check the selected ring before direct per-ring consumption. Perform both checks before honoring a zero record bound so invalid callback use always reports the error. Fixes: bf99c936f947 ("libbpf: Add BPF ring buffer support") Assisted-by: Codex:gpt-5.5 Signed-off-by: Tamir Duberstein --- tools/lib/bpf/libbpf.h | 11 ++- tools/lib/bpf/ringbuf.c | 43 +++++++++-- tools/testing/selftests/bpf/prog_tests/ringbuf.c | 93 ++++++++++++++++++++++++ 3 files changed, 136 insertions(+), 11 deletions(-) diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index bba4e8464396..9ba6b9ad3498 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -1526,18 +1526,17 @@ LIBBPF_API int ring__map_fd(const struct ring *r); * * @param r A ringbuffer object. * @return The number of records consumed (or INT_MAX, whichever is less), or - * a negative number if any of the callbacks return an error. + * a negative error code on failure. */ LIBBPF_API int ring__consume(struct ring *r); /** - * @brief **ring__consume_n()** consumes up to a requested amount of items from - * a ringbuffer without event polling. + * @brief **ring__consume_n()** consumes up to a requested number of records + * from a ringbuffer without event polling. * * @param r A ringbuffer object. - * @param n Maximum amount of items to consume. - * @return The number of items consumed, or a negative number if any of the - * callbacks return an error. + * @param n Maximum number of records to consume. + * @return The number of records consumed, or a negative error code on failure. */ LIBBPF_API int ring__consume_n(struct ring *r, size_t n); diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c index f2bb619d5a75..0dae4d95d309 100644 --- a/tools/lib/bpf/ringbuf.c +++ b/tools/lib/bpf/ringbuf.c @@ -231,6 +231,26 @@ static inline int roundup_len(__u32 len) return (len + 7) / 8 * 8; } +static int ringbuf_validate(const struct ring *r) +{ + if (unlikely(!r->sample_cb)) + return -EINVAL; + return 0; +} + +static int ringbuf_validate_callbacks(const struct ring_buffer *rb) +{ + int i, err; + + for (i = 0; i < rb->ring_cnt; i++) { + err = ringbuf_validate(rb->rings[i]); + if (err) + return err; + } + + return 0; +} + static int64_t ringbuf_process_ring(struct ring *r, size_t n) { int *len_ptr, len, err; @@ -240,6 +260,9 @@ static int64_t ringbuf_process_ring(struct ring *r, size_t n) bool got_new_data; void *sample; + err = ringbuf_validate(r); + if (err) + return err; if (n == 0) return 0; @@ -284,14 +307,17 @@ static int64_t ringbuf_process_ring(struct ring *r, size_t n) * records. * * Returns number of records consumed across all registered ring buffers (or - * n, whichever is less), or negative number if any of the callbacks return - * error. + * n, whichever is less), or a negative error code on failure. */ int ring_buffer__consume_n(struct ring_buffer *rb, size_t n) { int64_t err, res = 0; int i; + err = ringbuf_validate_callbacks(rb); + if (err) + return libbpf_err(err); + for (i = 0; i < rb->ring_cnt; i++) { struct ring *ring = rb->rings[i]; @@ -309,14 +335,17 @@ int ring_buffer__consume_n(struct ring_buffer *rb, size_t n) /* Consume available ring buffer(s) data without event polling. * 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_MAX, whichever is less), or a negative error code on failure. */ int ring_buffer__consume(struct ring_buffer *rb) { int64_t err, res = 0; int i; + err = ringbuf_validate_callbacks(rb); + if (err) + return libbpf_err(err); + for (i = 0; i < rb->ring_cnt; i++) { struct ring *ring = rb->rings[i]; @@ -334,13 +363,17 @@ int ring_buffer__consume(struct ring_buffer *rb) /* Poll for available data and consume records, if any are available. * Returns number of records consumed (or INT_MAX, whichever is less), or - * negative number, if any of the registered callbacks returned error. + * a negative error code on failure. */ int ring_buffer__poll(struct ring_buffer *rb, int timeout_ms) { int i, cnt; int64_t err, res = 0; + err = ringbuf_validate_callbacks(rb); + if (err) + return libbpf_err(err); + cnt = epoll_wait(rb->epoll_fd, rb->events, rb->ring_cnt, timeout_ms); if (cnt < 0) return libbpf_err(-errno); diff --git a/tools/testing/selftests/bpf/prog_tests/ringbuf.c b/tools/testing/selftests/bpf/prog_tests/ringbuf.c index 4f0558f14847..9ce996bcea8c 100644 --- a/tools/testing/selftests/bpf/prog_tests/ringbuf.c +++ b/tools/testing/selftests/bpf/prog_tests/ringbuf.c @@ -401,6 +401,97 @@ static int process_n_sample(void *ctx, void *data, size_t len) return 0; } +static int process_noop_sample(void *ctx, void *data, size_t len) +{ + return 0; +} + +static void ringbuf_null_cb_subtest(void) +{ + struct test_ringbuf_n_lskel *skel_n; + struct ring_buffer *ringbuf = NULL; + struct ring *ring; + unsigned long consumer_pos; + int no_cb_map_fd = -1; + int err; + + skel_n = test_ringbuf_n_lskel__open(); + if (!ASSERT_OK_PTR(skel_n, "test_ringbuf_n_lskel__open")) + return; + + skel_n->maps.ringbuf.max_entries = getpagesize(); + skel_n->bss->pid = getpid(); + skel_n->bss->value = SAMPLE_VALUE; + + err = test_ringbuf_n_lskel__load(skel_n); + if (!ASSERT_OK(err, "test_ringbuf_n_lskel__load")) + goto cleanup; + + err = test_ringbuf_n_lskel__attach(skel_n); + if (!ASSERT_OK(err, "test_ringbuf_n_lskel__attach")) + goto cleanup; + + syscall(__NR_getpgid); + + no_cb_map_fd = bpf_map_create(BPF_MAP_TYPE_RINGBUF, NULL, 0, 0, + getpagesize(), NULL); + if (!ASSERT_OK_FD(no_cb_map_fd, "bpf_map_create")) + goto cleanup; + + /* Manager APIs must validate all rings before consuming any of them. */ + ringbuf = ring_buffer__new(skel_n->maps.ringbuf.map_fd, + process_noop_sample, NULL, NULL); + if (!ASSERT_OK_PTR(ringbuf, "ring_buffer__new")) + goto cleanup_fd; + + ring = ring_buffer__ring(ringbuf, 0); + if (!ASSERT_OK_PTR(ring, "ring_buffer__ring")) + goto cleanup_ringbuf; + + err = ring_buffer__add(ringbuf, no_cb_map_fd, NULL, NULL); + if (!ASSERT_OK(err, "ring_buffer__add_no_cb")) + goto cleanup_ringbuf; + + consumer_pos = ring__consumer_pos(ring); + ASSERT_GT(ring__producer_pos(ring), consumer_pos, + "producer_pos_mixed_cb"); + + err = ring_buffer__consume_n(ringbuf, 0); + ASSERT_EQ(err, -EINVAL, "ringbuf_consume_zero_mixed_cb"); + err = ring_buffer__consume(ringbuf); + ASSERT_EQ(err, -EINVAL, "ringbuf_consume_mixed_cb"); + err = ring_buffer__poll(ringbuf, 0); + ASSERT_EQ(err, -EINVAL, "ringbuf_poll_mixed_cb"); + ASSERT_EQ(ring__consumer_pos(ring), consumer_pos, + "consumer_pos_mixed_cb"); + + ring_buffer__free(ringbuf); + ringbuf = + ring_buffer__new(skel_n->maps.ringbuf.map_fd, NULL, NULL, NULL); + if (!ASSERT_OK_PTR(ringbuf, "ring_buffer__new_no_cb")) + goto cleanup_fd; + + ring = ring_buffer__ring(ringbuf, 0); + if (!ASSERT_OK_PTR(ring, "ring_buffer__ring_no_cb")) + goto cleanup_ringbuf; + consumer_pos = ring__consumer_pos(ring); + + err = ring_buffer__consume_n(ringbuf, 0); + ASSERT_EQ(err, -EINVAL, "ringbuf_consume_zero_no_cb"); + err = ring__consume_n(ring, 0); + ASSERT_EQ(err, -EINVAL, "ring_consume_zero_no_cb"); + err = ring__consume(ring); + ASSERT_EQ(err, -EINVAL, "ring_consume_no_cb"); + ASSERT_EQ(ring__consumer_pos(ring), consumer_pos, "consumer_pos_no_cb"); + +cleanup_ringbuf: + ring_buffer__free(ringbuf); +cleanup_fd: + close(no_cb_map_fd); +cleanup: + test_ringbuf_n_lskel__destroy(skel_n); +} + static void ringbuf_n_subtest(void) { struct test_ringbuf_n_lskel *skel_n; @@ -579,6 +670,8 @@ void test_ringbuf(void) ringbuf_subtest(); if (test__start_subtest("ringbuf_n")) ringbuf_n_subtest(); + if (test__start_subtest("ringbuf_null_cb")) + ringbuf_null_cb_subtest(); if (test__start_subtest("ringbuf_map_key")) ringbuf_map_key_subtest(); if (test__start_subtest("ringbuf_write")) -- 2.55.0.rc0.159.gbe5d7338c2