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perf record: Fix event fd races

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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: <gthelen@google.com>
Reviewed-by: Leo Yan <leo.yan@linaro.org>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Anand K Mistry <amistry@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20221024011024.462518-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Ian Rogers 2022-10-23 18:10:24 -07:00 committed by Arnaldo Carvalho de Melo
parent f1bdebbb67
commit 304f0a2f6a
1 changed files with 25 additions and 16 deletions
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41
tools/perf/builtin-record.c
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@ -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);