From: Alexander Lobakin <alexandr.lobakin@intel.com>
To: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>
Cc: "Alexander Lobakin" <alexandr.lobakin@intel.com>,
"Toke Høiland-Jørgensen" <toke@redhat.com>,
"Martin KaFai Lau" <martin.lau@linux.dev>,
"Song Liu" <song@kernel.org>,
"Jesper Dangaard Brouer" <hawk@kernel.org>,
"Jakub Kicinski" <kuba@kernel.org>,
bpf@vger.kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: [PATCH bpf] bpf, test_run: fix &xdp_frame misplacement for LIVE_FRAMES
Date: Thu, 9 Feb 2023 18:28:27 +0100 [thread overview]
Message-ID: <20230209172827.874728-1-alexandr.lobakin@intel.com> (raw)
&xdp_buff and &xdp_frame are bound in a way that
xdp_buff->data_hard_start == xdp_frame
It's always the case and e.g. xdp_convert_buff_to_frame() relies on
this.
IOW, the following:
for (u32 i = 0; i < 0xdead; i++) {
xdpf = xdp_convert_buff_to_frame(&xdp);
xdp_convert_frame_to_buff(xdpf, &xdp);
}
shouldn't ever modify @xdpf's contents or the pointer itself.
However, "live packet" code wrongly treats &xdp_frame as part of its
context placed *before* the data_hard_start. With such flow,
data_hard_start is sizeof(*xdpf) off to the right and no longer points
to the XDP frame.
Instead of replacing `sizeof(ctx)` with `offsetof(ctx, xdpf)` in several
places and praying that there are no more miscalcs left somewhere in the
code, unionize ::frm with ::data in a flex array, so that both starts
pointing to the actual data_hard_start and the XDP frame actually starts
being a part of it, i.e. a part of the headroom, not the context.
A nice side effect is that the maximum frame size for this mode gets
increased by 40 bytes, as xdp_buff::frame_sz includes everything from
data_hard_start (-> includes xdpf already) to the end of XDP/skb shared
info.
(was found while testing XDP traffic generator on ice, which calls
xdp_convert_frame_to_buff() for each XDP frame)
Fixes: b530e9e1063e ("bpf: Add "live packet" mode for XDP in BPF_PROG_RUN")
Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>
---
net/bpf/test_run.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index 2723623429ac..c3cce7a8d47d 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -97,8 +97,11 @@ static bool bpf_test_timer_continue(struct bpf_test_timer *t, int iterations,
struct xdp_page_head {
struct xdp_buff orig_ctx;
struct xdp_buff ctx;
- struct xdp_frame frm;
- u8 data[];
+ union {
+ /* ::data_hard_start starts here */
+ DECLARE_FLEX_ARRAY(struct xdp_frame, frm);
+ DECLARE_FLEX_ARRAY(u8, data);
+ };
};
struct xdp_test_data {
@@ -132,7 +135,7 @@ static void xdp_test_run_init_page(struct page *page, void *arg)
headroom -= meta_len;
new_ctx = &head->ctx;
- frm = &head->frm;
+ frm = head->frm;
data = &head->data;
memcpy(data + headroom, orig_ctx->data_meta, frm_len);
@@ -223,7 +226,7 @@ static void reset_ctx(struct xdp_page_head *head)
head->ctx.data = head->orig_ctx.data;
head->ctx.data_meta = head->orig_ctx.data_meta;
head->ctx.data_end = head->orig_ctx.data_end;
- xdp_update_frame_from_buff(&head->ctx, &head->frm);
+ xdp_update_frame_from_buff(&head->ctx, head->frm);
}
static int xdp_recv_frames(struct xdp_frame **frames, int nframes,
@@ -285,7 +288,7 @@ static int xdp_test_run_batch(struct xdp_test_data *xdp, struct bpf_prog *prog,
head = phys_to_virt(page_to_phys(page));
reset_ctx(head);
ctx = &head->ctx;
- frm = &head->frm;
+ frm = head->frm;
xdp->frame_cnt++;
act = bpf_prog_run_xdp(prog, ctx);
--
2.39.1
next reply other threads:[~2023-02-09 17:30 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-09 17:28 Alexander Lobakin [this message]
2023-02-09 20:04 ` [PATCH bpf] bpf, test_run: fix &xdp_frame misplacement for LIVE_FRAMES Alexander Lobakin
2023-02-09 20:58 ` Toke Høiland-Jørgensen
2023-02-10 12:31 ` Alexander Lobakin
2023-02-10 13:19 ` Alexander Lobakin
2023-02-09 20:04 ` Toke Høiland-Jørgensen
2023-02-10 12:29 ` Alexander Lobakin
2023-02-10 17:38 ` Toke Høiland-Jørgensen
2023-02-13 14:03 ` Alexander Lobakin
2023-02-11 2:01 ` Jakub Kicinski
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