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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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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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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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