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| author | Benjamin Tissoires <bentiss@kernel.org> | 2024-06-26 15:46:26 +0200 |
|---|---|---|
| committer | Benjamin Tissoires <bentiss@kernel.org> | 2024-06-27 11:00:12 +0200 |
| commit | 75839101ce52e319cb2154a027d14f1f0aa3be09 (patch) | |
| tree | 37b05cb095474429cd80940e2c7b2e6d6d3a92a7 /include/linux/hid_bpf.h | |
| parent | 8bd0488b5ea58655ad6fdcbe0408ef49b16882b1 (diff) | |
| download | lwn-75839101ce52e319cb2154a027d14f1f0aa3be09.tar.gz lwn-75839101ce52e319cb2154a027d14f1f0aa3be09.zip | |
HID: bpf: prevent infinite recursions with hid_hw_raw_requests hooks
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.
Link: https://patch.msgid.link/20240626-hid_hw_req_bpf-v2-5-cfd60fb6c79f@kernel.org
Acked-by: Jiri Kosina <jkosina@suse.com>
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
Diffstat (limited to 'include/linux/hid_bpf.h')
| -rw-r--r-- | include/linux/hid_bpf.h | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/include/linux/hid_bpf.h b/include/linux/hid_bpf.h index 3c01f7f8b6fc..088c94b6d8ec 100644 --- a/include/linux/hid_bpf.h +++ b/include/linux/hid_bpf.h @@ -68,7 +68,7 @@ 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, @@ -181,7 +181,7 @@ 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); @@ -195,7 +195,7 @@ 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) {} |