From 304f0a2f6a6d9336fb5e474d7f62b8677d5ee167 Mon Sep 17 00:00:00 2001 From: Ian Rogers Date: Sun, 23 Oct 2022 18:10:24 -0700 Subject: perf record: Fix event fd races 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: Reviewed-by: Leo Yan Signed-off-by: Ian Rogers Cc: Alexander Shishkin Cc: Anand K Mistry Cc: Ingo Molnar Cc: Jiri Olsa Cc: Mark Rutland Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Stephane Eranian Link: https://lore.kernel.org/r/20221024011024.462518-1-irogers@google.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/builtin-record.c | 41 +++++++++++++++++++++++++---------------- 1 file changed, 25 insertions(+), 16 deletions(-) (limited to 'tools') 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 @@ out_free_threads: 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); -- cgit v1.2.3