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 bentiss@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) {}