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    Subject[PATCH] Fix: tracepoint: do not warn on ENOMEM
    Date
    Tracepoint should only warn when a kernel API user does not respect the
    required preconditions (e.g. same tracepoint enabled twice, or called
    to remove a tracepoint that does not exist).

    Silence warning in out-of-memory conditions, given that the error is
    returned to the caller.

    This ensures that out-of-memory error-injection testing does not trigger
    warnings in tracepoint.c, which were seen by syzbot.

    Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
    Reported-by: syzbot+9c0d616860575a73166a@syzkaller.appspotmail.com
    Reported-by: syzbot+4e9ae7fa46233396f64d@syzkaller.appspotmail.com
    CC: Steven Rostedt <rostedt@goodmis.org>
    CC: Ingo Molnar <mingo@redhat.com>
    CC: Peter Zijlstra <peterz@infradead.org>
    CC: Jiri Olsa <jolsa@redhat.com>
    CC: Arnaldo Carvalho de Melo <acme@kernel.org>
    CC: Alexander Shishkin <alexander.shishkin@linux.intel.com>
    CC: Namhyung Kim <namhyung@kernel.org>
    CC: stable@vger.kernel.org
    Link: https://lkml.kernel.org/r/001a114465e241a8720567419a72@google.com
    Link: https://lkml.kernel.org/r/001a1140e0de15fc910567464190@google.com
    ---
    kernel/tracepoint.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
    index 671b13457387..1e37da2e0c25 100644
    --- a/kernel/tracepoint.c
    +++ b/kernel/tracepoint.c
    @@ -207,7 +207,7 @@ static int tracepoint_add_func(struct tracepoint *tp,
    lockdep_is_held(&tracepoints_mutex));
    old = func_add(&tp_funcs, func, prio);
    if (IS_ERR(old)) {
    - WARN_ON_ONCE(1);
    + WARN_ON_ONCE(PTR_ERR(old) != -ENOMEM);
    return PTR_ERR(old);
    }

    @@ -239,7 +239,7 @@ static int tracepoint_remove_func(struct tracepoint *tp,
    lockdep_is_held(&tracepoints_mutex));
    old = func_remove(&tp_funcs, func);
    if (IS_ERR(old)) {
    - WARN_ON_ONCE(1);
    + WARN_ON_ONCE(PTR_ERR(old) != -ENOMEM);
    return PTR_ERR(old);
    }

    --
    2.11.0
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