perf/bpf: Fix data race in __perf_event_overflow - #8705
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perf_event_detach_bpf_prog() writes event->prog = NULL under bpf_event_mutex, while __perf_event_overflow() reads event->prog concurrently without any lock protection. This causes a data race detected by KCSAN. __perf_event_overflow() can be called from interrupt/NMI context, so it cannot acquire bpf_event_mutex. Fix the race by using WRITE_ONCE() in perf_event_detach_bpf_prog() and READ_ONCE() in __perf_event_overflow(). Also store the result of READ_ONCE() in a local variable to avoid reading event->prog twice which could result in a NULL pointer dereference if the pointer becomes NULL between the two reads. Reported-by: syzbot+651d2774bd1d8395595f@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=651d2774bd1d8395595f Fixes: f11f10b ("perf/bpf: Call BPF handler directly, not through overflow machinery") Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com> Reported-by: syzbot+651d2774bd1d8395595f@syzkaller.appspotmail.com Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com> Signed-off-by: appear twice. Also, the second Reported-by: is placed
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Pull request for series with
subject: perf/bpf: Fix data race in __perf_event_overflow
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=1144381