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Re: [Libguestfs] [PATCH libguestfs] guestfish: detect a few more failed syscalls



On 19/08/09 09:34, Jim Meyering wrote:
There were a few unchecked syscalls in fish.c

From ba8b8b0684a03b6e6fbb939ed7e1cbf5e1000092 Mon Sep 17 00:00:00 2001
From: Jim Meyering<meyering redhat com>
Date: Wed, 19 Aug 2009 10:01:07 +0200
Subject: [PATCH libguestfs] guestfish: detect a few more failed syscalls

* fish/fish.c (issue_command): Detect/diagnose more failed syscalls.
---
  fish/fish.c |   26 +++++++++++++++++++++-----
  1 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/fish/fish.c b/fish/fish.c
index 830617b..e6cd270 100644
--- a/fish/fish.c
+++ b/fish/fish.c
@@ -750,8 +750,14 @@ issue_command (const char *cmd, char *argv[], const char *pipecmd)
    if (pipecmd) {
      int fd[2];

-    fflush (stdout);
-    pipe (fd);
+    if (fflush (stdout)); {

Looks like a stray semicolon in there. Also, wouldn't it be better form to test for test for a return value of EOF?

+      perror ("failed to flush standard output");
+      return -1;
+    }
+    if (pipe (fd)) {
+      perror ("pipe failed");
+      return -1;
+    }

Again, I'd explicitly test for a return value of -1 for consistency.

      pid = fork ();
      if (pid == -1) {
        perror ("fork");
@@ -760,7 +766,10 @@ issue_command (const char *cmd, char *argv[], const char *pipecmd)

      if (pid == 0) {		/* Child process. */
        close (fd[1]);
-      dup2 (fd[0], 0);
+      if (dup2 (fd[0], 0)<  0) {
+        perror ("dup2 of stdin failed");
+        _exit (1);
+      }

fd[1] ought to be closed after this call. Not directly relevant to this patch, but '0' is a magic number. Use STDIN_FILENO from unistd.h.

        r = system (pipecmd);
        if (r == -1) {
@@ -770,9 +779,16 @@ issue_command (const char *cmd, char *argv[], const char *pipecmd)
        _exit (WEXITSTATUS (r));
      }

-    stdout_saved_fd = dup (1);
+    if ((stdout_saved_fd = dup (1))<  0) {
+      perror ("failed to dup stdout");
+      return -1;
+    }

'1' is a magic number. Use STDOUT_FILENO from unistd.h.

      close (fd[0]);
-    dup2 (fd[1], 1);
+    if (dup2 (fd[1], 1)) {
+      perror ("failed to dup stdout");
+      close (stdout_saved_fd);
+      return -1;
+    }

Test for return value of -1. '1' is a magic number.

      close (fd[1]);
    }

--
1.6.4.378.g88f2f

Matt
--
Matthew Booth, RHCA, RHCSS
Red Hat Engineering, Virtualisation Team

M:       +44 (0)7977 267231
GPG ID:  D33C3490
GPG FPR: 3733 612D 2D05 5458 8A8A 1600 3441 EA19 D33C 3490


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