ash: prevent leakage of process handlesHEADmaster

When the shell invoked process substitution it retained a process
handle to the child.  These handles could accumulate without limit.

The shell in upstream BusyBox doesn't bother to create a job
structure for process substitutions or here documents.  This isn't
appropriate on Windows, where we need to track the child process
handles.  Create job structures as required.

Saves 32-48 bytes.

(GitHub issue #587)

1 files changed, 7 insertions, 4 deletions

diff --git a/shell/ash.c b/shell/ash.c
index 0a63c434f..49556f256 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -6275,7 +6275,7 @@ forkshell(struct job *jp, union node *n, int mode)
 static int
 write2pipe(int pip[2], const char *p, size_t len)
 {
-        IF_PLATFORM_MINGW32(struct forkshell fs);
+        IF_PLATFORM_MINGW32(struct forkshell fs;)
 
         if (len <= PIPE_BUF) {
                 xwrite(pip[1], p, len);
@@ -6288,7 +6288,8 @@ write2pipe(int pip[2], const char *p, size_t len)
         fs.fd[0] = pip[0];
         fs.fd[1] = pip[1];
         fs.path = p;
-        spawn_forkshell(&fs, NULL, NULL, FORK_NOJOB);
+        // We need a job to track the process handle.
+        spawn_forkshell(&fs, makejob(1), NULL, FORK_NOJOB);
 #else
         if (forkshell((struct job *)NULL, (union node *)NULL, FORK_NOJOB) == 0) {
                 /* child */
@@ -7806,9 +7807,9 @@ evalbackcmd(union node *n, struct backcmd *result
 
         if (pipe(pip) < 0)
                 ash_msg_and_raise_perror("can't create pipe");
-        /* process substitution uses NULL job, like openhere() */
-        jp = (ctl == CTLBACKQ) ? makejob(1) : NULL;
 #if ENABLE_PLATFORM_MINGW32
+        // We need a job to track the process handle.
+        jp = makejob(1);
         memset(&fs, 0, sizeof(fs));
         fs.fpid = FS_EVALBACKCMD;
         fs.n = n;
@@ -7817,6 +7818,8 @@ evalbackcmd(union node *n, struct backcmd *result
         fs.fd[2] = ctl;
         spawn_forkshell(&fs, jp, n, FORK_NOJOB);
 #else
+        /* process substitution uses NULL job, like openhere() */
+        jp = (ctl == CTLBACKQ) ? makejob(1) : NULL;
         if (forkshell(jp, n, FORK_NOJOB) == 0) {
                 /* child */
                 reset_exception_handler();