From: Ian Rogers <irogers@google.com>
To: Greg Thelen <gthelen@google.com>,
Anand K Mistry <amistry@google.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@kernel.org>, Namhyung Kim <namhyung@kernel.org>,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Stephane Eranian <eranian@google.com>, Ian Rogers <irogers@google.com>
Subject: [PATCH v1] perf record: Fix event fd races
Date: Sun, 23 Oct 2022 18:10:24 -0700 [thread overview]
Message-ID: <20221024011024.462518-1-irogers@google.com> (raw)
The write call may set errno which is problematic if occurring in a
function also setting errno. Save and restore errno around the write
call.
done_fd may be used after close, clear it as part of the close and
check its validity in the signal handler.
Suggested-by: Greg Thelen <gthelen@google.com>
Signed-off-by: Ian Rogers <irogers@google.com>
---
tools/perf/builtin-record.c | 41 ++++++++++++++++++++++---------------
1 file changed, 25 insertions(+), 16 deletions(-)
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 52d254b1530c..e128b855ddde 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -649,7 +649,7 @@ static int record__pushfn(struct mmap *map, void *to, void *bf, size_t size)
static volatile int signr = -1;
static volatile int child_finished;
#ifdef HAVE_EVENTFD_SUPPORT
-static int done_fd = -1;
+static volatile int done_fd = -1;
#endif
static void sig_handler(int sig)
@@ -661,19 +661,24 @@ static void sig_handler(int sig)
done = 1;
#ifdef HAVE_EVENTFD_SUPPORT
-{
- u64 tmp = 1;
- /*
- * It is possible for this signal handler to run after done is checked
- * in the main loop, but before the perf counter fds are polled. If this
- * happens, the poll() will continue to wait even though done is set,
- * and will only break out if either another signal is received, or the
- * counters are ready for read. To ensure the poll() doesn't sleep when
- * done is set, use an eventfd (done_fd) to wake up the poll().
- */
- if (write(done_fd, &tmp, sizeof(tmp)) < 0)
- pr_err("failed to signal wakeup fd, error: %m\n");
-}
+ if (done_fd >= 0) {
+ u64 tmp = 1;
+ int orig_errno = errno;
+
+ /*
+ * It is possible for this signal handler to run after done is
+ * checked in the main loop, but before the perf counter fds are
+ * polled. If this happens, the poll() will continue to wait
+ * even though done is set, and will only break out if either
+ * another signal is received, or the counters are ready for
+ * read. To ensure the poll() doesn't sleep when done is set,
+ * use an eventfd (done_fd) to wake up the poll().
+ */
+ if (write(done_fd, &tmp, sizeof(tmp)) < 0)
+ pr_err("failed to signal wakeup fd, error: %m\n");
+
+ errno = orig_errno;
+ }
#endif // HAVE_EVENTFD_SUPPORT
}
@@ -2834,8 +2839,12 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
out_delete_session:
#ifdef HAVE_EVENTFD_SUPPORT
- if (done_fd >= 0)
- close(done_fd);
+ if (done_fd >= 0) {
+ fd = done_fd;
+ done_fd = -1;
+
+ close(fd);
+ }
#endif
zstd_fini(&session->zstd_data);
perf_session__delete(session);
--
2.38.0.135.g90850a2211-goog
next reply other threads:[~2022-10-24 1:10 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-24 1:10 Ian Rogers [this message]
2022-10-24 2:56 ` [PATCH v1] perf record: Fix event fd races Leo Yan
2022-10-24 5:33 ` Ian Rogers
2022-10-24 9:16 ` Leo Yan
2022-10-24 11:30 ` Arnaldo Carvalho de Melo
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