netdev - [PATCH bpf] bpf, test_run: Fix LIVE_FRAME frame update after a page has been recycled

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Message-Id: <20241030-test-run-mem-fix-v1-1-41e88e8cae43@redhat.com>
Date: Wed, 30 Oct 2024 11:48:26 +0100
From: Toke Høiland-Jørgensen <toke@...hat.com>
To: Alexei Starovoitov <ast@...nel.org>, 
 Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, 
 Martin KaFai Lau <martin.lau@...ux.dev>, 
 Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
 Yonghong Song <yonghong.song@...ux.dev>, 
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, 
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
 Jiri Olsa <jolsa@...nel.org>, "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
 Jesper Dangaard Brouer <hawk@...nel.org>, 
 Alexander Lobakin <aleksander.lobakin@...el.com>
Cc: bpf@...r.kernel.org, netdev@...r.kernel.org, 
 syzbot+d121e098da06af416d23@...kaller.appspotmail.com, 
 Toke Høiland-Jørgensen <toke@...hat.com>
Subject: [PATCH bpf] bpf, test_run: Fix LIVE_FRAME frame update after a
 page has been recycled

The test_run code detects whether a page has been modified and
re-initialises the xdp_frame structure if it has, using
xdp_update_frame_from_buff(). However, xdp_update_frame_from_buff()
doesn't touch frame->mem, so that wasn't correctly re-initialised, which
led to the pages from page_pool not being returned correctly. Syzbot
noticed this as a memory leak.

Fix this by also copying the frame->mem structure when re-initialising
the frame, like we do on initialisation of a new page from page_pool.

Reported-by: syzbot+d121e098da06af416d23@...kaller.appspotmail.com
Tested-by: syzbot+d121e098da06af416d23@...kaller.appspotmail.com
Fixes: e5995bc7e2ba ("bpf, test_run: fix crashes due to XDP frame overwriting/corruption")
Fixes: b530e9e1063e ("bpf: Add "live packet" mode for XDP in BPF_PROG_RUN")
Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
---
 net/bpf/test_run.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index 6d7a442ceb89be15501069655a51671d6ddfaf0e..501ec4249fedc3d34fe39aff50eea66f82b88a11 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -246,6 +246,7 @@ static void reset_ctx(struct xdp_page_head *head)
 	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->frame);
+	head->frame->mem = head->orig_ctx.rxq->mem;
 }

 static int xdp_recv_frames(struct xdp_frame **frames, int nframes,

---
base-commit: d0b98f6a17a5cb336121302bce0c97eb5fe32d16
change-id: 20241030-test-run-mem-fix-ac835c75ec3f

Best regards,
-- 
Toke Høiland-Jørgensen <toke@...hat.com>