Re: [PATCH v3 6/9] treewide: Suppress clang-tidy warning if we already use O_CLOEXEC or if we can't

[David Gibson <david@gibson.dropbear.id.au>]

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On Mon, Oct 28, 2024 at 11:00:41AM +0100, Stefano Brivio wrote:
> In pcap_init(), we should always open the packet capture file with
> O_CLOEXEC, even if we're not running in foreground: O_CLOEXEC means
> close-on-exec, not close-on-fork.
> 
> In logfile_init() and pidfile_open(), the fact that we pass a third
> 'mode' argument to open() seems to confuse the android-cloexec-open
> checker in LLVM versions from 16 to 19 (at least).
> 
> The checker is suggesting to add O_CLOEXEC to 'mode', and not in
> 'flags', where we already have it.

.. well.. the checker with the googletest package installed, anyway :/

> Add a suppression for clang-tidy and a comment, and avoid repeating
> those three time by adding a new helper, output_file_open().
> 
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  conf.c |  3 ++-
>  log.c  |  3 +--
>  pcap.c |  7 ++-----
>  util.c | 26 ++++++++++----------------
>  util.h |  2 +-
>  5 files changed, 16 insertions(+), 25 deletions(-)
> 
> diff --git a/conf.c b/conf.c
> index 4db7c64..b28f411 100644
> --- a/conf.c
> +++ b/conf.c
> @@ -1194,7 +1194,8 @@ static void conf_open_files(struct ctx *c)
>  	if (c->mode != MODE_PASTA && c->fd_tap == -1)
>  		c->fd_tap_listen = tap_sock_unix_open(c->sock_path);
>  
> -	c->pidfile_fd = pidfile_open(c->pidfile);
> +	if (*c->pidfile && (c->pidfile_fd = output_file_open(c->pidfile) < 0))
> +		die_perror("Couldn't open PID file %s", c->pidfile);
>  }
>  
>  /**
> diff --git a/log.c b/log.c
> index dd25862..48db4d9 100644
> --- a/log.c
> +++ b/log.c
> @@ -410,8 +410,7 @@ void logfile_init(const char *name, const char *path, size_t size)
>  	if (readlink("/proc/self/exe", exe, PATH_MAX - 1) < 0)
>  		die_perror("Failed to read own /proc/self/exe link");
>  
> -	log_file = open(path, O_CREAT | O_TRUNC | O_RDWR | O_CLOEXEC,
> -			S_IRUSR | S_IWUSR);
> +	log_file = output_file_open(path);
>  	if (log_file == -1)
>  		die_perror("Couldn't open log file %s", path);
>  
> diff --git a/pcap.c b/pcap.c
> index 6ee6cdf..a07eb33 100644
> --- a/pcap.c
> +++ b/pcap.c
> @@ -158,18 +158,15 @@ void pcap_iov(const struct iovec *iov, size_t iovcnt, size_t offset)
>   */
>  void pcap_init(struct ctx *c)
>  {
> -	int flags = O_WRONLY | O_CREAT | O_TRUNC;
> -
>  	if (pcap_fd != -1)
>  		return;
>  
>  	if (!*c->pcap)
>  		return;
>  
> -	flags |= c->foreground ? O_CLOEXEC : 0;
> -	pcap_fd = open(c->pcap, flags, S_IRUSR | S_IWUSR);
> +	pcap_fd = output_file_open(c->pcap);
>  	if (pcap_fd == -1) {
> -		perror("open");
> +		err_perror("Couldn't open pcap file %s", c->pcap);
>  		return;
>  	}
>  
> diff --git a/util.c b/util.c
> index 9cb705e..d838b34 100644
> --- a/util.c
> +++ b/util.c
> @@ -407,25 +407,19 @@ void pidfile_write(int fd, pid_t pid)
>  }
>  
>  /**
> - * pidfile_open() - Open PID file if needed
> - * @path:	Path for PID file, empty string if no PID file is requested
> + * output_file_open() - Open file for output, if needed
> + * @path:	Path for output file
>   *
> - * Return: descriptor for PID file, -1 if path is NULL, won't return on failure
> + * Return: file descriptor on success, -1 on failure with errno set by open()
>   */
> -int pidfile_open(const char *path)
> +int output_file_open(const char *path)
>  {
> -	int fd;
> -
> -	if (!*path)
> -		return -1;
> -
> -	if ((fd = open(path, O_CREAT | O_TRUNC | O_WRONLY | O_CLOEXEC,
> -			     S_IRUSR | S_IWUSR)) < 0) {
> -		perror("PID file open");
> -		exit(EXIT_FAILURE);
> -	}
> -
> -	return fd;
> +	/* We use O_CLOEXEC here, but clang-tidy as of LLVM 16 to 19 looks for
> +	 * it in the 'mode' argument if we have one
> +	 */
> +	return open(path, O_CREAT | O_TRUNC | O_WRONLY | O_CLOEXEC,
> +		    /* NOLINTNEXTLINE(android-cloexec-open) */
> +		    S_IRUSR | S_IWUSR);
>  }
>  
>  /**
> diff --git a/util.h b/util.h
> index 4f8b768..73b4a49 100644
> --- a/util.h
> +++ b/util.h
> @@ -193,7 +193,7 @@ char *line_read(char *buf, size_t len, int fd);
>  void ns_enter(const struct ctx *c);
>  bool ns_is_init(void);
>  int open_in_ns(const struct ctx *c, const char *path, int flags);
> -int pidfile_open(const char *path);
> +int output_file_open(const char *path);
>  void pidfile_write(int fd, pid_t pid);
>  int __daemon(int pidfile_fd, int devnull_fd);
>  int fls(unsigned long x);

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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