[CRIU] [RFC PATCH] util: shutdown log in cr_system_userns if error fd is negative

[Pavel Emelyanov]

On 04/22/2016 01:20 PM, Stanislav Kinsburskiy wrote:
> Otherwise error in case of exec error won't be printed
> The problem is that when err fd is negative, it's replaced by log fd.
> Then err is moved to STDERR (that means, that log_fd is _closed_).

Why, log fd is service fd, not STDERR one.

> But log facility still consider log fd as valid and tries to use it to print
> error message in case of exec failure.
> Which is equal to writing to /dev/null, basically.
> This patch shutdown log, if err fd was negative, thus forcing criu to output
> exec error to STDERR (which was replaced by log fs, btw).

Not necessarily it's replaced by logfd, err can be specified.

> 
> Signed-off-by: Stanislav Kinsburskiy <skinsbursky at virtuozzo.com>
> ---
>  criu/util.c |    9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/criu/util.c b/criu/util.c
> index 4f88309..dae6031 100644
> --- a/criu/util.c
> +++ b/criu/util.c
> @@ -609,6 +609,8 @@ int cr_system_userns(int in, int out, int err, char *cmd,
>  		pr_perror("fork() failed");
>  		goto out;
>  	} else if (pid == 0) {
> +		bool stop_log_fd = false;
> +
>  		if (userns_pid > 0) {
>  			if (switch_ns(userns_pid, &user_ns_desc, NULL))
>  				goto out_chld;
> @@ -620,8 +622,10 @@ int cr_system_userns(int in, int out, int err, char *cmd,
>  
>  		if (out < 0)
>  			out = log_get_fd();
> -		if (err < 0)
> +		if (err < 0) {
>  			err = log_get_fd();
> +			stop_log_fd = true;
> +		}
>  
>  		/*
>  		 * out, err, in should be a separate fds,
> @@ -637,6 +641,9 @@ int cr_system_userns(int in, int out, int err, char *cmd,
>  		    move_img_fd(&err, STDIN_FILENO))
>  			goto out_chld;
>  
> +		if (stop_log_fd)
> +			log_fini();
> +
>  		if (in < 0) {
>  			close(STDIN_FILENO);
>  		} else {
> 
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