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 actually fetch
data from the device itself.
However, this means that we might enter an infinite loop between
hid_hw_raw_requests hooks and hid_bpf_hw_request() call.
To prevent that, if a hid_bpf_hw_request() call is emitted, we prevent
any new call of this kfunc by storing the information in the context.
This way we can always trace/monitor/filter the incoming bpf requests,
while preventing those loops to happen.
I don't think exposing "from_bpf" is very interesting because while
writing such a bpf program, you need to match at least the report number
and/or the source of the call. So a blind "if there is a
hid_hw_raw_request() call, I'm emitting another one" makes no real
sense.
Signed-off-by: Benjamin Tissoires <bent...@kernel.org>
---
drivers/hid/bpf/hid_bpf_dispatch.c | 12 ++++++++++--
drivers/hid/bpf/hid_bpf_dispatch.h | 1 +
drivers/hid/hid-core.c | 6 +++---
drivers/hid/hidraw.c | 4 ++--
include/linux/hid.h | 2 +-
include/linux/hid_bpf.h | 6 +++---
6 files changed, 20 insertions(+), 11 deletions(-)
diff --git a/drivers/hid/bpf/hid_bpf_dispatch.c
b/drivers/hid/bpf/hid_bpf_dispatch.c
index 813b53119b85..8d6e08b7c42f 100644
--- a/drivers/hid/bpf/hid_bpf_dispatch.c
+++ b/drivers/hid/bpf/hid_bpf_dispatch.c
@@ -78,7 +78,7 @@ int 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 = {
@@ -87,6 +87,7 @@ int dispatch_hid_bpf_raw_requests(struct hid_device *hdev,
.size = size,
},
.data = buf,
+ .from_bpf = from_bpf,
};
struct hid_bpf_ops *e;
int ret;
@@ -362,11 +363,17 @@ __bpf_kfunc int
hid_bpf_hw_request(struct hid_bpf_ctx *ctx, __u8 *buf, size_t buf__sz,
enum hid_report_type rtype, enum hid_class_request reqtype)
{
+ struct hid_bpf_ctx_kern *ctx_kern;
struct hid_device *hdev;
size_t size = buf__sz;
u8 *dma_data;
int ret;
+ ctx_kern = container_of(ctx, struct hid_bpf_ctx_kern, ctx);
+
+ if (ctx_kern->from_bpf)
+ return -EDEADLOCK;
+
/* check arguments */
ret = __hid_bpf_hw_check_params(ctx, buf, &size, rtype);
if (ret)
@@ -396,7 +403,8 @@ 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/bpf/hid_bpf_dispatch.h
b/drivers/hid/bpf/hid_bpf_dispatch.h
index 835e6f69f479..44c6ea22233f 100644
--- a/drivers/hid/bpf/hid_bpf_dispatch.h
+++ b/drivers/hid/bpf/hid_bpf_dispatch.h
@@ -8,6 +8,7 @@
struct hid_bpf_ctx_kern {
struct hid_bpf_ctx ctx;
u8 *data;
+ bool from_bpf;
};
struct hid_device *hid_get_device(unsigned int hid_id);
diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index d839cfdf1624..0164aacf07ac 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -2403,7 +2403,7 @@ 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;
int ret;
@@ -2415,7 +2415,7 @@ int __hid_hw_raw_request(struct hid_device *hdev,
return -EINVAL;
ret = dispatch_hid_bpf_raw_requests(hdev, reportnum, buf, len, rtype,
- reqtype, source);
+ reqtype, source, from_bpf);
if (ret)
return ret;
@@ -2441,7 +2441,7 @@ 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 5c3f179dc2ab..bb6cc5c7c705 100644
--- a/include/linux/hid_bpf.h
+++ b/include/linux/hid_bpf.h
@@ -67,7 +67,7 @@ struct hid_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,
@@ -178,7 +178,7 @@ int 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);
@@ -192,7 +192,7 @@ static inline int 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 0; }
+ u64 source, bool from_bpf) {
return 0; }
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
