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Fri, 18 Mar 2022 14:10:11 -0700 (PDT) MIME-Version: 1.0 References: <20220318161528.1531164-1-benjamin.tissoires@redhat.com> <20220318161528.1531164-7-benjamin.tissoires@redhat.com> In-Reply-To: <20220318161528.1531164-7-benjamin.tissoires@redhat.com> From: Song Liu Date: Fri, 18 Mar 2022 14:10:00 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH bpf-next v3 06/17] HID: allow to change the report descriptor from an eBPF program To: Benjamin Tissoires Cc: Greg KH , Jiri Kosina , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Shuah Khan , Dave Marchevsky , Joe Stringer , Jonathan Corbet , Tero Kristo , open list , "open list:HID CORE LAYER" , Networking , bpf , linux-kselftest@vger.kernel.org, Linux Doc Mailing List Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 18, 2022 at 9:17 AM Benjamin Tissoires wrote: > > Make use of BPF_HID_ATTACH_RDESC_FIXUP so we can trigger an rdesc fixup > in the bpf world. > > Whenever the program gets attached/detached, the device is reconnected > meaning that userspace will see it disappearing and reappearing with > the new report descriptor. > > Signed-off-by: Benjamin Tissoires > > --- > > changes in v3: > - ensure the ctx.size is properly bounded by allocated size > - s/link_attached/post_link_attach/ > - removed the switch statement with only one case > > changes in v2: > - split the series by bpf/libbpf/hid/selftests and samples > --- > drivers/hid/hid-bpf.c | 62 ++++++++++++++++++++++++++++++++++++++++++ > drivers/hid/hid-core.c | 3 +- > include/linux/hid.h | 6 ++++ > 3 files changed, 70 insertions(+), 1 deletion(-) > > diff --git a/drivers/hid/hid-bpf.c b/drivers/hid/hid-bpf.c > index 5060ebcb9979..45c87ff47324 100644 > --- a/drivers/hid/hid-bpf.c > +++ b/drivers/hid/hid-bpf.c > @@ -50,6 +50,14 @@ static struct hid_device *hid_bpf_fd_to_hdev(int fd) > return hdev; > } > > +static int hid_reconnect(struct hid_device *hdev) > +{ > + if (!test_and_set_bit(ffs(HID_STAT_REPROBED), &hdev->status)) > + return device_reprobe(&hdev->dev); > + > + return 0; > +} > + > static int hid_bpf_pre_link_attach(struct hid_device *hdev, enum bpf_hid_attach_type type) > { > int err = 0; > @@ -92,6 +100,12 @@ static int hid_bpf_pre_link_attach(struct hid_device *hdev, enum bpf_hid_attach_ > return err; > } > > +static void hid_bpf_post_link_attach(struct hid_device *hdev, enum bpf_hid_attach_type type) > +{ > + if (type == BPF_HID_ATTACH_RDESC_FIXUP) > + hid_reconnect(hdev); > +} > + > static void hid_bpf_array_detach(struct hid_device *hdev, enum bpf_hid_attach_type type) > { > switch (type) { > @@ -99,6 +113,9 @@ static void hid_bpf_array_detach(struct hid_device *hdev, enum bpf_hid_attach_ty > kfree(hdev->bpf.device_data); > hdev->bpf.device_data = NULL; > break; > + case BPF_HID_ATTACH_RDESC_FIXUP: > + hid_reconnect(hdev); > + break; > default: > /* do nothing */ > break; > @@ -116,6 +133,9 @@ static int hid_bpf_run_progs(struct hid_device *hdev, struct hid_bpf_ctx_kern *c > case HID_BPF_DEVICE_EVENT: > type = BPF_HID_ATTACH_DEVICE_EVENT; > break; > + case HID_BPF_RDESC_FIXUP: > + type = BPF_HID_ATTACH_RDESC_FIXUP; > + break; > default: > return -EINVAL; > } > @@ -155,11 +175,53 @@ u8 *hid_bpf_raw_event(struct hid_device *hdev, u8 *data, int *size) > return ctx.data; > } > > +u8 *hid_bpf_report_fixup(struct hid_device *hdev, u8 *rdesc, unsigned int *size) > +{ > + int ret; > + struct hid_bpf_ctx_kern ctx = { > + .type = HID_BPF_RDESC_FIXUP, > + .hdev = hdev, > + .size = *size, > + }; > + > + if (bpf_hid_link_empty(&hdev->bpf, BPF_HID_ATTACH_RDESC_FIXUP)) Do we need to lock bpf_hid_mutex before calling bpf_hid_link_empty()? (or maybe we already did?) > + goto ignore_bpf; > + > + ctx.data = kmemdup(rdesc, HID_MAX_DESCRIPTOR_SIZE, GFP_KERNEL); > + if (!ctx.data) > + goto ignore_bpf; > + > + ctx.allocated_size = HID_MAX_DESCRIPTOR_SIZE; > + > + ret = hid_bpf_run_progs(hdev, &ctx); > + if (ret) > + goto ignore_bpf; > + > + if (ctx.size > ctx.allocated_size) > + goto ignore_bpf; > + > + *size = ctx.size; > + > + if (*size) { > + rdesc = krealloc(ctx.data, *size, GFP_KERNEL); > + } else { > + rdesc = NULL; > + kfree(ctx.data); > + } > + > + return rdesc; > + > + ignore_bpf: > + kfree(ctx.data); > + return kmemdup(rdesc, *size, GFP_KERNEL); > +} > + > int __init hid_bpf_module_init(void) > { > struct bpf_hid_hooks hooks = { > .hdev_from_fd = hid_bpf_fd_to_hdev, > .pre_link_attach = hid_bpf_pre_link_attach, > + .post_link_attach = hid_bpf_post_link_attach, > .array_detach = hid_bpf_array_detach, > }; > > diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c > index 937fab7eb9c6..3182c39db006 100644 > --- a/drivers/hid/hid-core.c > +++ b/drivers/hid/hid-core.c > @@ -1213,7 +1213,8 @@ int hid_open_report(struct hid_device *device) > return -ENODEV; > size = device->dev_rsize; > > - buf = kmemdup(start, size, GFP_KERNEL); > + /* hid_bpf_report_fixup() ensures we work on a copy of rdesc */ > + buf = hid_bpf_report_fixup(device, start, &size); > if (buf == NULL) > return -ENOMEM; > > diff --git a/include/linux/hid.h b/include/linux/hid.h > index 8fd79011f461..66d949d10b78 100644 > --- a/include/linux/hid.h > +++ b/include/linux/hid.h > @@ -1213,10 +1213,16 @@ do { \ > > #ifdef CONFIG_BPF > u8 *hid_bpf_raw_event(struct hid_device *hdev, u8 *rd, int *size); > +u8 *hid_bpf_report_fixup(struct hid_device *hdev, u8 *rdesc, unsigned int *size); > int hid_bpf_module_init(void); > void hid_bpf_module_exit(void); > #else > static inline u8 *hid_bpf_raw_event(struct hid_device *hdev, u8 *rd, int *size) { return rd; } > +static inline u8 *hid_bpf_report_fixup(struct hid_device *hdev, u8 *rdesc, > + unsigned int *size) > +{ > + return kmemdup(rdesc, *size, GFP_KERNEL); > +} > static inline int hid_bpf_module_init(void) { return 0; } > static inline void hid_bpf_module_exit(void) {} > #endif > -- > 2.35.1 >