diff options
| 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 /drivers/hid/bpf/hid_bpf_dispatch.c | |
| 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 'drivers/hid/bpf/hid_bpf_dispatch.c')
| -rw-r--r-- | drivers/hid/bpf/hid_bpf_dispatch.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/drivers/hid/bpf/hid_bpf_dispatch.c b/drivers/hid/bpf/hid_bpf_dispatch.c index 37a1bb381684..61c02538e591 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, idx; @@ -364,11 +365,17 @@ __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) @@ -398,7 +405,8 @@ 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); |