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

Commit Message

Toke Høiland-Jørgensen Oct. 30, 2024, 10:48 a.m. UTC

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: [e-mail]
Tested-by: [e-mail]
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 <[e-mail]>
---
 net/bpf/test_run.c | 1 +
 1 file changed, 1 insertion(+)


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

Best regards,

Comments

Stanislav Fomichev Oct. 30, 2024, 2:43 p.m. UTC | #1

On 10/30, Toke Høiland-Jørgensen wrote:
> 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: [e-mail]
> Tested-by: [e-mail]
> 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 <[e-mail]>

Acked-by: Stanislav Fomichev <[e-mail]>

Alexander Lobakin Oct. 30, 2024, 3:54 p.m. UTC | #2

From: Toke Høiland-Jørgensen <[e-mail]>
Date: Wed, 30 Oct 2024 11:48:26 +0100

> 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: [e-mail]
> Tested-by: [e-mail]
> 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 <[e-mail]>

Reviewed-by: Alexander Lobakin <[e-mail]>

Thanks,
Olek

[e-mail] Oct. 31, 2024, 3:30 p.m. UTC | #3

Hello:

This patch was applied to bpf/bpf.git (master)
by Daniel Borkmann <[e-mail]>:

On Wed, 30 Oct 2024 11:48:26 +0100 you wrote:
> 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.
> 
> [...]

Here is the summary with links:
  - [bpf] bpf, test_run: Fix LIVE_FRAME frame update after a page has been recycled
    https://git.kernel.org/bpf/bpf/c/c40dd8c47325

You are awesome, thank you!

Patch

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,