On Thu, Sep 14, 2023 at 4:12 PM Martin Kelly
<martin.kelly@xxxxxxxxxxxxxxx> wrote:
>
> Refactor the cleanup code in ring_buffer__add to use a unified err_out
> label. This reduces code duplication, as well as plugging a potential
> leak if mmap_sz != (__u64)(size_t)mmap_sz (currently this would miss
> unmapping tmp because ringbuf_unmap_ring isn't called).
>
> Signed-off-by: Martin Kelly <martin.kelly@xxxxxxxxxxxxxxx>
> ---
> tools/lib/bpf/ringbuf.c | 19 ++++++++++---------
> 1 file changed, 10 insertions(+), 9 deletions(-)
>
> diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c
> index 02199364db13..f2020807996c 100644
> --- a/tools/lib/bpf/ringbuf.c
> +++ b/tools/lib/bpf/ringbuf.c
> @@ -118,10 +118,9 @@ int ring_buffer__add(struct ring_buffer *rb, int map_fd,
> /* Map writable consumer page */
> tmp = mmap(NULL, rb->page_size, PROT_READ | PROT_WRITE, MAP_SHARED, map_fd, 0);
> if (tmp == MAP_FAILED) {
> - err = -errno;
removing this is wrong, pr_warn() can clobber errno
> pr_warn("ringbuf: failed to mmap consumer page for map fd=%d: %d\n",
> map_fd, err);
> - return libbpf_err(err);
> + goto err_out;
> }
> r->consumer_pos = tmp;
>
> @@ -131,16 +130,15 @@ int ring_buffer__add(struct ring_buffer *rb, int map_fd,
> */
> mmap_sz = rb->page_size + 2 * (__u64)info.max_entries;
> if (mmap_sz != (__u64)(size_t)mmap_sz) {
> + errno = E2BIG;
ditto, stick to err
> pr_warn("ringbuf: ring buffer size (%u) is too big\n", info.max_entries);
> - return libbpf_err(-E2BIG);
> + goto err_out;
> }
> tmp = mmap(NULL, (size_t)mmap_sz, PROT_READ, MAP_SHARED, map_fd, rb->page_size);
> if (tmp == MAP_FAILED) {
> - err = -errno;
> - ringbuf_unmap_ring(rb, r);
> pr_warn("ringbuf: failed to mmap data pages for map fd=%d: %d\n",
> map_fd, err);
> - return libbpf_err(err);
> + goto err_out;
> }
> r->producer_pos = tmp;
> r->data = tmp + rb->page_size;
> @@ -151,15 +149,18 @@ int ring_buffer__add(struct ring_buffer *rb, int map_fd,
> e->events = EPOLLIN;
> e->data.fd = rb->ring_cnt;
> if (epoll_ctl(rb->epoll_fd, EPOLL_CTL_ADD, map_fd, e) < 0) {
> - err = -errno;
> - ringbuf_unmap_ring(rb, r);
> pr_warn("ringbuf: failed to epoll add map fd=%d: %d\n",
> map_fd, err);
> - return libbpf_err(err);
> + goto err_out;
> }
>
> rb->ring_cnt++;
> return 0;
> +
> +err_out:
> + err = -errno;
> + ringbuf_unmap_ring(rb, r);
> + return libbpf_err(err);
> }
>
> void ring_buffer__free(struct ring_buffer *rb)
> --
> 2.34.1
>
