From 473f742e1845d83dbbd1a32e3881c3d36ae99ea1 Mon Sep 17 00:00:00 2001 From: Namhyung Kim Date: Tue, 2 Feb 2021 18:01:18 +0900 Subject: [PATCH] perf tools: Use scandir() to iterate threads when synthesizing PERF_RECORD_ events Like in __event__synthesize_thread(), I think it's better to use scandir() instead of the readdir() loop. In case some malicious task continues to create new threads, the readdir() loop will run over and over to collect tids. The scandir() also has the problem but the window is much smaller since it doesn't do much work during the iteration. Also add filter_task() function as we only care the tasks. Signed-off-by: Namhyung Kim Acked-by: Jiri Olsa Cc: Alexander Shishkin Cc: Andi Kleen Cc: Ian Rogers Cc: Ingo Molnar Cc: Mark Rutland Cc: Peter Zijlstra Cc: Stephane Eranian Link: https://lore.kernel.org/r/20210202090118.2008551-4-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/synthetic-events.c | 28 +++++++++++++++++----------- 1 file changed, 17 insertions(+), 11 deletions(-) diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c index abea688..fcec775 100644 --- a/tools/perf/util/synthetic-events.c +++ b/tools/perf/util/synthetic-events.c @@ -704,6 +704,11 @@ int perf_event__synthesize_modules(struct perf_tool *tool, perf_event__handler_t return rc; } +static int filter_task(const struct dirent *dirent) +{ + return isdigit(dirent->d_name[0]); +} + static int __event__synthesize_thread(union perf_event *comm_event, union perf_event *mmap_event, union perf_event *fork_event, @@ -712,10 +717,10 @@ static int __event__synthesize_thread(union perf_event *comm_event, struct perf_tool *tool, struct machine *machine, bool mmap_data) { char filename[PATH_MAX]; - DIR *tasks; - struct dirent *dirent; + struct dirent **dirent; pid_t tgid, ppid; int rc = 0; + int i, n; /* special case: only send one comm event using passed in pid */ if (!full) { @@ -747,18 +752,16 @@ static int __event__synthesize_thread(union perf_event *comm_event, snprintf(filename, sizeof(filename), "%s/proc/%d/task", machine->root_dir, pid); - tasks = opendir(filename); - if (tasks == NULL) { - pr_debug("couldn't open %s\n", filename); - return 0; - } + n = scandir(filename, &dirent, filter_task, alphasort); + if (n < 0) + return n; - while ((dirent = readdir(tasks)) != NULL) { + for (i = 0; i < n; i++) { char *end; pid_t _pid; bool kernel_thread; - _pid = strtol(dirent->d_name, &end, 10); + _pid = strtol(dirent[i]->d_name, &end, 10); if (*end) continue; @@ -791,7 +794,10 @@ static int __event__synthesize_thread(union perf_event *comm_event, } } - closedir(tasks); + for (i = 0; i < n; i++) + zfree(&dirent[i]); + free(dirent); + return rc; } @@ -976,7 +982,7 @@ int perf_event__synthesize_threads(struct perf_tool *tool, return 0; snprintf(proc_path, sizeof(proc_path), "%s/proc", machine->root_dir); - n = scandir(proc_path, &dirent, 0, alphasort); + n = scandir(proc_path, &dirent, filter_task, alphasort); if (n < 0) return err; -- 2.7.4