Re: [Qemu-devel] [PATCH 1.1] qemu-ga: fix segv after failure to open log file

[Peter Maydell <peter.maydell@linaro.org>]

On 14 May 2012 23:04, Michael Roth <mdroth@linux.vnet.ibm.com> wrote:
> Currently, if we fail to open the specified log file (generally due to a
> permissions issue), we'll assign NULL to the logfile handle (stderr,
> initially) used by the logging routines, which can cause a segfault to
> occur when we attempt to report the error before exiting.
>
> Instead, only re-assign if the open() was successful.
>
> Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
> ---
>  qemu-ga.c |    6 ++++--
>  1 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/qemu-ga.c b/qemu-ga.c
> index 3a88333..e2725c8 100644
> --- a/qemu-ga.c
> +++ b/qemu-ga.c
> @@ -681,6 +681,7 @@ int main(int argc, char **argv)
>     const char *log_filepath = NULL;
>     const char *pid_filepath = QGA_PIDFILE_DEFAULT;
>     const char *state_dir = QGA_STATEDIR_DEFAULT;
> +    FILE *log_file;
>  #ifdef _WIN32
>     const char *service = NULL;
>  #endif
> @@ -836,12 +837,13 @@ int main(int argc, char **argv)
>             become_daemon(pid_filepath);
>         }
>         if (log_filepath) {
> -            s->log_file = fopen(log_filepath, "a");
> -            if (!s->log_file) {
> +            log_file = fopen(log_filepath, "a");
> +            if (!log_file) {
>                 g_critical("unable to open specified log file: %s",
>                            strerror(errno));
>                 goto out_bad;
>             }
> +            s->log_file = log_file;
>         }
>     }

It would be nicer to put the log_file variable definition
inside the if(), rather than putting it 150 lines earlier
in the source file...

-- PMM