linux-kernel - [PATCH 4.9 12/32] tracepoint: Do not warn on ENOMEM

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Date:   Tue,  8 May 2018 10:10:52 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
        Jiri Olsa <jolsa@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        syzbot+9c0d616860575a73166a@...kaller.appspotmail.com,
        syzbot+4e9ae7fa46233396f64d@...kaller.appspotmail.com,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>
Subject: [PATCH 4.9 12/32] tracepoint: Do not warn on ENOMEM

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>

commit d66a270be3310d7aa132fec0cea77d3d32a0ff75 upstream.

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.

Link: https://lkml.kernel.org/r/001a114465e241a8720567419a72@google.com
Link: https://lkml.kernel.org/r/001a1140e0de15fc910567464190@google.com
Link: http://lkml.kernel.org/r/20180315124424.32319-1-mathieu.desnoyers@efficios.com

CC: Peter Zijlstra <peterz@...radead.org>
CC: Jiri Olsa <jolsa@...hat.com>
CC: Arnaldo Carvalho de Melo <acme@...nel.org>
CC: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
CC: Namhyung Kim <namhyung@...nel.org>
CC: stable@...r.kernel.org
Fixes: de7b2973903c6 ("tracepoint: Use struct pointer instead of name hash for reg/unreg tracepoints")
Reported-by: syzbot+9c0d616860575a73166a@...kaller.appspotmail.com
Reported-by: syzbot+4e9ae7fa46233396f64d@...kaller.appspotmail.com
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/tracepoint.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -202,7 +202,7 @@ static int tracepoint_add_func(struct tr
 			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);
 	}
 
@@ -235,7 +235,7 @@ static int tracepoint_remove_func(struct
 			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);
 	}