linux-kernel - [PATCH HID v2 01/13] HID: bpf: fix dispatch_hid_bpf_device

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Message-Id: <20240626-hid_hw_req_bpf-v2-1-cfd60fb6c79f@kernel.org>
Date: Wed, 26 Jun 2024 15:46:22 +0200
From: Benjamin Tissoires <bentiss@...nel.org>
To: Jiri Kosina <jikos@...nel.org>, Alexei Starovoitov <ast@...nel.org>, 
 Shuah Khan <shuah@...nel.org>, Jonathan Corbet <corbet@....net>
Cc: linux-input@...r.kernel.org, linux-kernel@...r.kernel.org, 
 bpf@...r.kernel.org, linux-kselftest@...r.kernel.org, 
 linux-doc@...r.kernel.org, Benjamin Tissoires <bentiss@...nel.org>, 
 Dan Carpenter <dan.carpenter@...aro.org>
Subject: [PATCH HID v2 01/13] HID: bpf: fix dispatch_hid_bpf_device_event
 uninitialized ret value

Looks like if a bpf program gets inserted and then removed,
hdev->bpf.device_data is then allocated, but the loop iterating
over the bpf program is never assigning ret.

This is a problem and also revealed another bug in which only the last
value of ret was checked. This effectively meant than only the last
program in the chain could change the size of the incoming buffer.

Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
Link: https://lore.kernel.org/all/00f7b624-219f-4a05-a7ad-5335f15a41c7@moroto.mountain
Fixes: 4a86220e046d ("HID: bpf: remove tracing HID-BPF capability")
Signed-off-by: Benjamin Tissoires <bentiss@...nel.org>

---

no changes in v2
---
 drivers/hid/bpf/hid_bpf_dispatch.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/bpf/hid_bpf_dispatch.c b/drivers/hid/bpf/hid_bpf_dispatch.c
index 06cc628e7bb4..b7b11a7c69db 100644
--- a/drivers/hid/bpf/hid_bpf_dispatch.c
+++ b/drivers/hid/bpf/hid_bpf_dispatch.c
@@ -57,11 +57,12 @@ dispatch_hid_bpf_device_event(struct hid_device *hdev, enum hid_report_type type
 			}
 
 			if (ret)
-				ctx_kern.ctx.retval = ret;
+				ctx_kern.ctx.size = ret;
 		}
 	}
 	rcu_read_unlock();
 
+	ret = ctx_kern.ctx.size;
 	if (ret) {
 		if (ret > ctx_kern.ctx.allocated_size)
 			return ERR_PTR(-EINVAL);

-- 
2.44.0