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Turns out that I got my reference counts wrong and each successful
bus_find_device() actually calls get_device(), and we need to manually
call put_device().
Ensure each bus_find_device() gets a matching put_device() when releasing
the bpf programs and fix all the error paths.
Cc: <stable@vger.kernel.org>
Fixes: f5c27da4e3c8 ("HID: initial BPF implementation")
Link: https://lore.kernel.org/r/20240124-b4-hid-bpf-fixes-v2-2-052520b1e5e6@kernel.org
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
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When the kfunc hid_bpf_attach_prog() is called, we called twice fdget():
one for fetching the type of the bpf program, and one for actually
attaching the program to the device.
The problem is that between those two calls, we have no guarantees that
the prog_fd is still the same file descriptor for the given program.
Solve this by calling bpf_prog_get() earlier, and use this to fetch the
program type.
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/bpf/CAO-hwJJ8vh8JD3-P43L-_CLNmPx0hWj44aom0O838vfP4=_1CA@mail.gmail.com/T/#t
Cc: <stable@vger.kernel.org>
Fixes: f5c27da4e3c8 ("HID: initial BPF implementation")
Link: https://lore.kernel.org/r/20240124-b4-hid-bpf-fixes-v2-1-052520b1e5e6@kernel.org
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
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We don't need to watch for calls on bpf_prog_put_deferred(), so remove
that from the entrypoints.bpf.c file.
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
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Previously, HID-BPF was relying on a bpf tracing program to be notified
when a program was released from userspace. This is error prone, as
LLVM sometimes inline the function and sometimes not.
So instead of messing up with the bpf prog ref count, we can use the
bpf_link concept which actually matches exactly what we want:
- a bpf_link represents the fact that a given program is attached to a
given HID device
- as long as the bpf_link has fd opened (either by the userspace program
still being around or by pinning the bpf object in the bpffs), the
program stays attached to the HID device
- once every user has closed the fd, we get called by
hid_bpf_link_release() that we no longer have any users, and we can
disconnect the program to the device in 2 passes: first atomically clear
the bit saying that the link is active, and then calling release_work in
a scheduled work item.
This solves entirely the problems of BPF tracing not showing up and is
definitely cleaner.
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
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Now that we have aproper non debug API to declare which function is
fmodret, we can rely on it.
Link: https://lore.kernel.org/all/20221121104403.1545f9b5@gandalf.local.home/
Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Link: https://lore.kernel.org/r/20221206145936.922196-3-benjamin.tissoires@redhat.com
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Add a new tracepoint hid_bpf_rdesc_fixup() so we can trigger a
report descriptor 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.
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
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We need to also be able to change the size of the report.
Reducing it is easy, because we already have the incoming buffer that is
big enough, but extending it is harder.
Pre-allocate a buffer that is big enough to handle all reports of the
device, and use that as the primary buffer for BPF programs.
To be able to change the size of the buffer, we change the device_event
API and request it to return the size of the buffer.
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
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Kind of a hack, but works for now:
Instead of listening for any close of eBPF program, we now
decrement the refcount when we insert it in our internal
map of fd progs.
This is safe to do because:
- we listen to any call of destructor of programs
- when a program is being destroyed, we disable it by removing
it from any RCU list used by any HID device (so it will never
be called)
- we then trigger a job to cleanup the prog fd map, but we overwrite
the removal of the elements to not do anything on the programs, just
remove the allocated space
This is better than previously because we can remove the map of known
programs and their usage count. We now rely on the refcount of
bpf, which has greater chances of being accurate.
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
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Declare an entry point that can use fmod_ret BPF programs, and
also an API to access and change the incoming data.
A simpler implementation would consist in just calling
hid_bpf_device_event() for any incoming event and let users deal
with the fact that they will be called for any event of any device.
The goal of HID-BPF is to partially replace drivers, so this situation
can be problematic because we might have programs which will step on
each other toes.
For that, we add a new API hid_bpf_attach_prog() that can be called
from a syscall and we manually deal with a jump table in hid-bpf.
Whenever we add a program to the jump table (in other words, when we
attach a program to a HID device), we keep the number of time we added
this program in the jump table so we can release it whenever there are
no other users.
HID devices have an RCU protected list of available programs in the
jump table, and those programs are called one after the other thanks
to bpf_tail_call().
To achieve the detection of users losing their fds on the programs we
attached, we add 2 tracing facilities on bpf_prog_release() (for when
a fd is closed) and bpf_free_inode() (for when a pinned program gets
unpinned).
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
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