Fix race condition in makedirs()

libc/x/makedirs.c

@@ -16,11 +16,11 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/intrin/safemacros.internal.h"
-#include "libc/intrin/weaken.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/strace.internal.h"
 #include "libc/errno.h"
+#include "libc/intrin/safemacros.internal.h"
+#include "libc/intrin/weaken.h"
 #include "libc/mem/mem.h"
 #include "libc/str/str.h"
 #include "libc/x/x.h"
@@ -44,7 +44,12 @@ static int MakeDirs(const char *path, unsigned mode, int e) {
   free(dir);
   if (rc == -1) return -1;
   errno = e;
-  return mkdir(path, mode);
+  if (!mkdir(path, mode) || errno == EEXIST) {
+    errno = e;
+    return 0;
+  } else {
+    return -1;
+  }
 }
 
 /**
@@ -55,7 +60,7 @@ static int MakeDirs(const char *path, unsigned mode, int e) {
  * @param path is a UTF-8 string, preferably relative w/ forward slashes
  * @param mode can be, for example, 0755
  * @return 0 on success or -1 w/ errno
- * @see mkdir()
+ * @threadsafe
  */
 int makedirs(const char *path, unsigned mode) {
   return MakeDirs(path, mode, errno);

libc/x/xbasename.c

@@ -17,6 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/fmt/conv.h"
+#include "libc/mem/mem.h"
 #include "libc/runtime/gc.internal.h"
 #include "libc/x/x.h"
 
@@ -24,5 +25,9 @@
  * Returns base portion of path.
  */
 char *xbasename(const char *path) {
-  return xstrdup(basename(gc(xstrdup(path))));
+  char *base;
+  path = xstrdup(path);
+  base = xstrdup(basename(path));
+  free(path);
+  return base;
 }

libc/x/xdirname.c

@@ -17,12 +17,16 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/fmt/conv.h"
-#include "libc/runtime/gc.internal.h"
+#include "libc/mem/mem.h"
 #include "libc/x/x.h"
 
 /**
  * Returns directory portion of path.
  */
 char *xdirname(const char *path) {
-  return xstrdup(dirname(gc(xstrdup(path))));
+  char *dirp;
+  path = xstrdup(path);
+  dirp = xstrdup(dirname(path));
+  free(path);
+  return dirp;
 }

test/libc/x/makedirs_test.c

@@ -0,0 +1,45 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2022 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/intrin/pthread.h"
+#include "libc/mem/mem.h"
+#include "libc/runtime/gc.internal.h"
+#include "libc/testlib/testlib.h"
+#include "libc/thread/spawn.h"
+#include "libc/x/x.h"
+
+#define DIR                                                                    \
+  "a/b/c/d/e/f/g/h/i/j/k/l/m/n/o/p/q/r/s/t/u/v/w/x/y/z/A/B/C/D/E/F/G/H/I/J/K/" \
+  "L/M/N/O/P/Q/R/S/T/U/V/W/X/Y/Z"
+
+pthread_barrier_t barrier;
+char testlib_enable_tmp_setup_teardown;
+
+int Worker(void *arg, int tid) {
+  pthread_barrier_wait(&barrier);
+  ASSERT_EQ(0, makedirs(DIR, 0755));
+  return 0;
+}
+
+TEST(makedirs, test) {
+  int i, n = 8;
+  struct spawn *t = gc(malloc(sizeof(struct spawn) * n));
+  ASSERT_EQ(0, pthread_barrier_init(&barrier, 0, n));
+  for (i = 0; i < n; ++i) ASSERT_SYS(0, 0, _spawn(Worker, 0, t + i));
+  for (i = 0; i < n; ++i) EXPECT_SYS(0, 0, _join(t + i));
+}

test/libc/x/test.mk

@@ -34,6 +34,7 @@ TEST_LIBC_X_DIRECTDEPS =			\
 	LIBC_SOCK				\
 	LIBC_STUBS				\
 	LIBC_SYSV				\
+	LIBC_THREAD				\
 	LIBC_TESTLIB				\
 	LIBC_X					\
 	THIRD_PARTY_GDTOA

tool/build/compile.c

@@ -47,6 +47,7 @@
 #include "libc/runtime/sysconf.h"
 #include "libc/stdio/append.internal.h"
 #include "libc/stdio/stdio.h"
+#include "libc/str/errfun.h"
 #include "libc/str/str.h"
 #include "libc/sysv/consts/auxv.h"
 #include "libc/sysv/consts/clock.h"
@@ -576,20 +577,37 @@ char *AddShellQuotes(const char *s) {
   return p;
 }
 
+void MakeDirs(const char *path, int mode) {
+  if (makedirs(path, mode)) {
+    kprintf("error: makedirs(%#s) failed\n", path);
+    exit(1);
+  }
+}
+
 int Launch(void) {
   size_t got;
   ssize_t rc;
   int ws, pid;
   uint64_t us;
   gotchld = 0;
-  if (pipe2(pipefds, O_CLOEXEC) == -1) exit(errno);
+
+  if (pipe2(pipefds, O_CLOEXEC) == -1) {
+    kprintf("pipe2 failed: %s\n", strerrno(errno));
+    exit(1);
+  }
+
   clock_gettime(CLOCK_MONOTONIC, &start);
   if (timeout > 0) {
     timer.it_value.tv_sec = timeout;
     timer.it_interval.tv_sec = timeout;
     setitimer(ITIMER_REAL, &timer, 0);
   }
+
   pid = vfork();
+  if (pid == -1) {
+    kprintf("vfork failed: %s\n", strerrno(errno));
+    exit(1);
+  }
 
 #if 0
   int fd;
@@ -611,9 +629,11 @@ int Launch(void) {
     dup2(pipefds[1], 2);
     sigprocmask(SIG_SETMASK, &savemask, 0);
     execve(cmd, args.p, env.p);
+    kprintf("execve(%#s) failed: %s\n", cmd, strerrno(errno));
     _Exit(127);
   }
   close(pipefds[1]);
+
   for (;;) {
     if (gotchld) {
       rc = 0;
@@ -1139,7 +1159,7 @@ int main(int argc, char *argv[]) {
   if (outpath) {
     outdir = xdirname(outpath);
     if (!isdirectory(outdir)) {
-      makedirs(outdir, 0755);
+      MakeDirs(outdir, 0755);
     }
   }
 
@@ -1190,7 +1210,7 @@ int main(int argc, char *argv[]) {
     if (WIFEXITED(ws)) {
       if (!(exitcode = WEXITSTATUS(ws)) || exitcode == 254) {
         if (touchtarget && target) {
-          makedirs(xdirname(target), 0755);
+          MakeDirs(xdirname(target), 0755);
           if (touch(target, 0644)) {
             exitcode = 90;
             appends(&output, "\nfailed to touch output file\n");