[PATCH 6.1 047/127] bpf, cpumap: Handle skb as well when clean up ptr_ring

Greg Kroah-Hartman
2023-08-09T10:53:22Z

From: Hou Tao <houtao1@huawei.com>

[ Upstream commit 7c62b75cd1a792e14b037fa4f61f9b18914e7de1 ]

The following warning was reported when running xdp_redirect_cpu with
both skb-mode and stress-mode enabled:

------------[ cut here ]------------
Incorrect XDP memory type (-2128176192) usage
WARNING: CPU: 7 PID: 1442 at net/core/xdp.c:405
Modules linked in:
CPU: 7 PID: 1442 Comm: kworker/7:0 Tainted: G 6.5.0-rc2+ #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
Workqueue: events __cpu_map_entry_free
RIP: 0010:__xdp_return+0x1e4/0x4a0
......
Call Trace:
<TASK>
? show_regs+0x65/0x70
? __warn+0xa5/0x240
? __xdp_return+0x1e4/0x4a0
......
xdp_return_frame+0x4d/0x150
__cpu_map_entry_free+0xf9/0x230
process_one_work+0x6b0/0xb80
worker_thread+0x96/0x720
kthread+0x1a5/0x1f0
ret_from_fork+0x3a/0x70
ret_from_fork_asm+0x1b/0x30
</TASK>

The reason for the warning is twofold. One is due to the kthread
cpu_map_kthread_run() is stopped prematurely. Another one is
__cpu_map_ring_cleanup() doesn't handle skb mode and treats skbs in
ptr_ring as XDP frames.

Prematurely-stopped kthread will be fixed by the preceding patch and
ptr_ring will be empty when __cpu_map_ring_cleanup() is called. But
as the comments in __cpu_map_ring_cleanup() said, handling and freeing
skbs in ptr_ring as well to "catch any broken behaviour gracefully".

Fixes: 11941f8a8536 ("bpf: cpumap: Implement generic cpumap")
Signed-off-by: Hou Tao <houtao1@huawei.com>
Acked-by: Jesper Dangaard Brouer <hawk@kernel.org>
Link: https://lore.kernel.org/r/20230729095107.1722450-3-houtao@huaweicloud.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/bpf/cpumap.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
index 09141351d5457..e5888d401d799 100644
--- a/kernel/bpf/cpumap.c
+++ b/kernel/bpf/cpumap.c
@@ -134,11 +134,17 @@ static void __cpu_map_ring_cleanup(struct ptr_ring *ring)
* invoked cpu_map_kthread_stop(). Catch any broken behaviour
* gracefully and warn once.
*/
- struct xdp_frame *xdpf;
+ void *ptr;

- while ((xdpf = ptr_ring_consume(ring)))
- if (WARN_ON_ONCE(xdpf))
- xdp_return_frame(xdpf);
+ while ((ptr = ptr_ring_consume(ring))) {
+ WARN_ON_ONCE(1);
+ if (unlikely(__ptr_test_bit(0, &ptr))) {
+ __ptr_clear_bit(0, &ptr);
+ kfree_skb(ptr);
+ continue;
+ }
+ xdp_return_frame(ptr);
+ }
}

static void put_cpu_map_entry(struct bpf_cpu_map_entry *rcpu)
--
2.40.1