[systemd-devel] [PATCH] random-seed: Avoid errors (and unit failure) when we cannot write random-seed file.

[David Herrmann]

Hi

On Mon, Jan 12, 2015 at 9:40 PM, Colin Guthrie <colin at mageia.org> wrote:
> When we call 'systemd-random-seed load' with a read-only /var/lib/systemd,
> the cleanup code (which rewrites the random-seed file) will fail and exit.
>
> Arguably, if the filesystem is read-only and the random-seed file exists
> then this will be possibly be quite bad for entroy on subsequent reboots
> but it should still not make the unit fail.

Applied!

Thanks
David

> ---
>  src/random-seed/random-seed.c | 24 ++++++++++++++----------
>  1 file changed, 14 insertions(+), 10 deletions(-)
>
> diff --git a/src/random-seed/random-seed.c b/src/random-seed/random-seed.c
> index 06c1239..99497d6 100644
> --- a/src/random-seed/random-seed.c
> +++ b/src/random-seed/random-seed.c
> @@ -38,6 +38,7 @@ int main(int argc, char *argv[]) {
>          ssize_t k;
>          int r;
>          FILE *f;
> +        bool cleanup_seed_file = true;
>
>          if (argc != 2) {
>                  log_error("This program requires one argument.");
> @@ -90,6 +91,7 @@ int main(int argc, char *argv[]) {
>                                  r = -errno;
>                                  goto finish;
>                          }
> +                        cleanup_seed_file = false;
>                  }
>
>                  random_fd = open("/dev/urandom", O_RDWR|O_CLOEXEC|O_NOCTTY, 0600);
> @@ -143,17 +145,19 @@ int main(int argc, char *argv[]) {
>          /* This is just a safety measure. Given that we are root and
>           * most likely created the file ourselves the mode and owner
>           * should be correct anyway. */
> -        fchmod(seed_fd, 0600);
> -        fchown(seed_fd, 0, 0);
> +        if (cleanup_seed_file) {
> +                fchmod(seed_fd, 0600);
> +                fchown(seed_fd, 0, 0);
>
> -        k = loop_read(random_fd, buf, buf_size, false);
> -        if (k <= 0) {
> -                log_error("Failed to read new seed from /dev/urandom: %s", r < 0 ? strerror(-r) : "EOF");
> -                r = k == 0 ? -EIO : (int) k;
> -        } else {
> -                r = loop_write(seed_fd, buf, (size_t) k, false);
> -                if (r < 0)
> -                        log_error_errno(r, "Failed to write new random seed file: %m");
> +                k = loop_read(random_fd, buf, buf_size, false);
> +                if (k <= 0) {
> +                        log_error("Failed to read new seed from /dev/urandom: %s", r < 0 ? strerror(-r) : "EOF");
> +                        r = k == 0 ? -EIO : (int) k;
> +                } else {
> +                        r = loop_write(seed_fd, buf, (size_t) k, false);
> +                        if (r < 0)
> +                                log_error_errno(r, "Failed to write new random seed file: %m");
> +                }
>          }
>
>  finish:
> --
> 2.2.1
>
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