From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752481AbbFDIoa (ORCPT ); Thu, 4 Jun 2015 04:44:30 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47819 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752103AbbFDIoY (ORCPT ); Thu, 4 Jun 2015 04:44:24 -0400 From: Milos Vyletel To: Peter Zijlstra , Paul Mackerras , Ingo Molnar , Arnaldo Carvalho de Melo , Jiri Olsa , Don Zickus , Andy Shevchenko , Milos Vyletel , "Steven Rostedt (Red Hat)" , linux-kernel@vger.kernel.org (open list:PERFORMANCE EVENT...) Subject: [PATCH] perf tools: avoid possible race condition in copyfile Date: Thu, 4 Jun 2015 10:44:12 +0200 Message-Id: <1433407453-28739-1-git-send-email-milos@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Use unique temporary files when copying to buildid dir to prevent races in case multiple instances are trying to copy same file. This is done by - creating template in form /..XXXXXX where the suffix is used by mkstemp() to create unique file - change file mode - copy content - if successful link temp file to target file - unlink temp file At this point the only file left at target path should be the desired one either created by us or other instance if we raced. This should also prevent not yet fully copied files to be visible to to other perf instances that could try to parse them. On top of that slow_copyfile no longer needs to deal with file mode when creating file since temporary file is already created and mode is set. Signed-off-by: Milos Vyletel --- tools/perf/util/util.c | 48 ++++++++++++++++++++++++++++++++---------------- 1 file changed, 32 insertions(+), 16 deletions(-) diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c index 4ee6d0d..fec1e13 100644 --- a/tools/perf/util/util.c +++ b/tools/perf/util/util.c @@ -72,20 +72,17 @@ int mkdir_p(char *path, mode_t mode) return (stat(path, &st) && mkdir(path, mode)) ? -1 : 0; } -static int slow_copyfile(const char *from, const char *to, mode_t mode) +static int slow_copyfile(const char *from, const char *to) { int err = -1; char *line = NULL; size_t n; FILE *from_fp = fopen(from, "r"), *to_fp; - mode_t old_umask; if (from_fp == NULL) goto out; - old_umask = umask(mode ^ 0777); to_fp = fopen(to, "w"); - umask(old_umask); if (to_fp == NULL) goto out_fclose_from; @@ -108,36 +105,55 @@ int copyfile_mode(const char *from, const char *to, mode_t mode) struct stat st; void *addr; int err = -1; + char *tmp = NULL, *ptr = NULL; if (stat(from, &st)) goto out; - if (st.st_size == 0) /* /proc? do it slowly... */ - return slow_copyfile(from, to, mode); - - fromfd = open(from, O_RDONLY); - if (fromfd < 0) + /* extra 'x' at the end is to reserve space for '.' */ + if (asprintf(&tmp, "%s.XXXXXXx", to) < 0) { + tmp = NULL; goto out; + } + ptr = strrchr(tmp, '/'); + if (!ptr) + goto out; + ptr = memmove(ptr + 1, ptr, strlen(ptr) - 1); + *ptr = '.'; - tofd = creat(to, mode); + tofd = mkstemp(tmp); if (tofd < 0) - goto out_close_from; + goto out; + + if (fchmod(tofd, mode)) + goto out_close_to; + + if (st.st_size == 0) { /* /proc? do it slowly... */ + err = slow_copyfile(from, tmp); + goto out_close_to; + } + + fromfd = open(from, O_RDONLY); + if (fromfd < 0) + goto out_close_to; addr = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fromfd, 0); if (addr == MAP_FAILED) - goto out_close_to; + goto out_close_from; if (write(tofd, addr, st.st_size) == st.st_size) err = 0; munmap(addr, st.st_size); -out_close_to: - close(tofd); - if (err) - unlink(to); out_close_from: close(fromfd); +out_close_to: + close(tofd); + if (!err) + err = link(tmp, to); + unlink(tmp); out: + free(tmp); return err; } -- 2.4.2