tree eb0522bdbb70a44f7942f8636da2b36f54f50ac6
parent a27758ffaf96f89002129eedb2cc172d254099f8
author Daniel Borkmann <daniel@iogearbox.net> 1465066259 +0200
committer David S. Miller <davem@davemloft.net> 1465336083 -0700

bpf, trace: use READ_ONCE for retrieving file ptr

In bpf_perf_event_read() and bpf_perf_event_output(), we must use
READ_ONCE() for fetching the struct file pointer, which could get
updated concurrently, so we must prevent the compiler from potential
refetching.

We already do this with tail calls for fetching the related bpf_prog,
but not so on stored perf events. Semantics for both are the same
with regards to updates.

Fixes: a43eec304259 ("bpf: introduce bpf_perf_event_output() helper")
Fixes: 35578d798400 ("bpf: Implement function bpf_perf_event_read() that get the selected hardware PMU conuter")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>