[PATCH RFC HID 7/7] HID: bpf: prevent infinite recursions with hid_hw_raw_requests hooks
From: Benjamin Tissoires
Date: Wed May 08 2024 - 06:29:20 EST
When we attach a sleepable hook to hid_hw_raw_requests, we can (and in
many cases should) call ourself hid_bpf_raw_request(), to actaully fetch
data from the device itself.
However, this means that we might enter an infinite loop between
hid_hw_raw_requests trace and hid_bpf_raw_request() call.
To prevent that, if a hid_bpf_raw_request() call is emitted, we prevent
any sleepable bpf trace to hid_hw_raw_requests(). This way we can always
trace/monitor/filter the incoming bpf requests, while preventing those
loops to happen.
Signed-off-by: Benjamin Tissoires <bentiss@xxxxxxxxxx>
---
drivers/hid/bpf/hid_bpf_dispatch.c | 7 ++++---
drivers/hid/hid-core.c | 6 +++---
drivers/hid/hidraw.c | 4 ++--
include/linux/hid.h | 2 +-
include/linux/hid_bpf.h | 6 +++---
5 files changed, 13 insertions(+), 12 deletions(-)
diff --git a/drivers/hid/bpf/hid_bpf_dispatch.c b/drivers/hid/bpf/hid_bpf_dispatch.c
index 7aeab3f9f2c7..79cac293ba29 100644
--- a/drivers/hid/bpf/hid_bpf_dispatch.c
+++ b/drivers/hid/bpf/hid_bpf_dispatch.c
@@ -99,7 +99,7 @@ dispatch_hid_bpf_raw_requests(struct hid_device *hdev,
unsigned char reportnum, u8 *buf,
u32 *size, enum hid_report_type rtype,
enum hid_class_request reqtype,
- u64 source)
+ u64 source, bool from_bpf)
{
struct hid_bpf_ctx_kern ctx_kern = {
.ctx = {
@@ -122,7 +122,7 @@ dispatch_hid_bpf_raw_requests(struct hid_device *hdev,
// if (!hdev->bpf.device_data)
// return buf;
- ret = hid_bpf_prog_run(hdev, HID_BPF_PROG_TYPE_RAW_REQUEST, &ctx_kern, true);
+ ret = hid_bpf_prog_run(hdev, HID_BPF_PROG_TYPE_RAW_REQUEST, &ctx_kern, !from_bpf);
if (ret < 0)
return ERR_PTR(ret);
@@ -536,7 +536,8 @@ hid_bpf_hw_request(struct hid_bpf_ctx *ctx, __u8 *buf, size_t buf__sz,
size,
rtype,
reqtype,
- (__u64)ctx);
+ (__u64)ctx,
+ true); /* prevent infinite recursions */
if (ret > 0)
memcpy(buf, dma_data, ret);
diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 7d468f6dbefe..d53f465a4ccb 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -2404,7 +2404,7 @@ int __hid_hw_raw_request(struct hid_device *hdev,
unsigned char reportnum, __u8 *buf,
size_t len, enum hid_report_type rtype,
enum hid_class_request reqtype,
- __u64 source)
+ __u64 source, bool from_bpf)
{
unsigned int max_buffer_size = HID_MAX_BUFFER_SIZE;
u32 size = (u32)len; /* max_buffer_size is 16 KB */
@@ -2416,7 +2416,7 @@ int __hid_hw_raw_request(struct hid_device *hdev,
return -EINVAL;
buf = dispatch_hid_bpf_raw_requests(hdev, reportnum, buf, &size, rtype,
- reqtype, source);
+ reqtype, source, from_bpf);
if (IS_ERR(buf))
return PTR_ERR(buf);
@@ -2442,7 +2442,7 @@ int hid_hw_raw_request(struct hid_device *hdev,
unsigned char reportnum, __u8 *buf,
size_t len, enum hid_report_type rtype, enum hid_class_request reqtype)
{
- return __hid_hw_raw_request(hdev, reportnum, buf, len, rtype, reqtype, 0);
+ return __hid_hw_raw_request(hdev, reportnum, buf, len, rtype, reqtype, 0, false);
}
EXPORT_SYMBOL_GPL(hid_hw_raw_request);
diff --git a/drivers/hid/hidraw.c b/drivers/hid/hidraw.c
index 6d2a6d38e42a..4ba3131de614 100644
--- a/drivers/hid/hidraw.c
+++ b/drivers/hid/hidraw.c
@@ -151,7 +151,7 @@ static ssize_t hidraw_send_report(struct file *file, const char __user *buffer,
}
ret = __hid_hw_raw_request(dev, buf[0], buf, count, report_type,
- HID_REQ_SET_REPORT, (__u64)file);
+ HID_REQ_SET_REPORT, (__u64)file, false);
out_free:
kfree(buf);
@@ -228,7 +228,7 @@ static ssize_t hidraw_get_report(struct file *file, char __user *buffer, size_t
}
ret = __hid_hw_raw_request(dev, report_number, buf, count, report_type,
- HID_REQ_GET_REPORT, (__u64)file);
+ HID_REQ_GET_REPORT, (__u64)file, false);
if (ret < 0)
goto out_free;
diff --git a/include/linux/hid.h b/include/linux/hid.h
index dac2804b4562..24d0d7c0bd33 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -1129,7 +1129,7 @@ int __hid_hw_raw_request(struct hid_device *hdev,
unsigned char reportnum, __u8 *buf,
size_t len, enum hid_report_type rtype,
enum hid_class_request reqtype,
- __u64 source);
+ __u64 source, bool from_bpf);
int __hid_hw_output_report(struct hid_device *hdev, __u8 *buf, size_t len, __u64 source);
int hid_hw_raw_request(struct hid_device *hdev,
unsigned char reportnum, __u8 *buf,
diff --git a/include/linux/hid_bpf.h b/include/linux/hid_bpf.h
index 1cd36bfdd608..6b2ac815572c 100644
--- a/include/linux/hid_bpf.h
+++ b/include/linux/hid_bpf.h
@@ -105,7 +105,7 @@ struct hid_bpf_ops {
unsigned char reportnum, __u8 *buf,
size_t len, enum hid_report_type rtype,
enum hid_class_request reqtype,
- __u64 source);
+ __u64 source, bool from_bpf);
int (*hid_hw_output_report)(struct hid_device *hdev, __u8 *buf, size_t len,
__u64 source);
int (*hid_input_report)(struct hid_device *hid, enum hid_report_type type,
@@ -148,7 +148,7 @@ u8 *dispatch_hid_bpf_raw_requests(struct hid_device *hdev,
unsigned char reportnum, __u8 *buf,
u32 *size, enum hid_report_type rtype,
enum hid_class_request reqtype,
- __u64 source);
+ __u64 source, bool from_bpf);
int hid_bpf_connect_device(struct hid_device *hdev);
void hid_bpf_disconnect_device(struct hid_device *hdev);
void hid_bpf_destroy_device(struct hid_device *hid);
@@ -162,7 +162,7 @@ static inline u8 *dispatch_hid_bpf_raw_requests(struct hid_device *hdev,
unsigned char reportnum, u8 *buf,
u32 *size, enum hid_report_type rtype,
enum hid_class_request reqtype,
- u64 source) { return buf; }
+ u64 source, bool from_bpf) { return buf; }
static inline int hid_bpf_connect_device(struct hid_device *hdev) { return 0; }
static inline void hid_bpf_disconnect_device(struct hid_device *hdev) {}
static inline void hid_bpf_destroy_device(struct hid_device *hid) {}
--
2.44.0