On Fri, Nov 17, 2017 at 08:44:33AM -0800, Steven Smith wrote:
> get_logname() assumes that when it calls read() it initializes c and
> errno, which isn't always true if we hit a whitelisted error or end of
> file. This occasionally shows up as agetty going into an infinite
> loop. Fix it by just delaying ten seconds and exiting when things go
> wrong, similarly to the behavior after a non-whitelisted error.
>
> Signed-off-by: Steven Smith <sos22@xxxxxxxxxxxxx>
> ---
> term-utils/agetty.c | 21 ++++++++++++++++-----
> 1 file changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/term-utils/agetty.c b/term-utils/agetty.c
> index 9763fcd30..bc848a25a 100644
> --- a/term-utils/agetty.c
> +++ b/term-utils/agetty.c
> @@ -317,6 +317,7 @@ static void termio_final(struct options *op,
> static int caps_lock(char *s);
> static speed_t bcode(char *s);
> static void usage(void) __attribute__((__noreturn__));
> +static void exit_slowly(int code) __attribute__((__noreturn__));
> static void log_err(const char *, ...) __attribute__((__noreturn__))
> __attribute__((__format__(printf, 1, 2)));
> static void log_warn (const char *, ...)
> @@ -1983,9 +1984,11 @@ static char *get_logname(struct options *op, struct termios *tp, struct chardata
> while (cp->eol == '\0') {
>
> char key;
> + ssize_t readres;
>
> debug("read from FD\n");
> - if (read(STDIN_FILENO, &c, 1) < 1) {
> + readres = read(STDIN_FILENO, &c, 1);
> + if (readres < 0) {
> debug("read failed\n");
>
> /* The terminal could be open with O_NONBLOCK when
> @@ -2000,12 +2003,15 @@ static char *get_logname(struct options *op, struct termios *tp, struct chardata
> case ESRCH:
> case EINVAL:
> case ENOENT:
> - break;
> + exit_slowly(EXIT_SUCCESS);
OK, makes sense.
> default:
> log_err(_("%s: read: %m"), op->tty);
> }
> }
>
> + if (readres == 0)
> + exit_slowly(EXIT_SUCCESS);
I'm not sure about it. Maybe it would be better to assume that readres == 0
and no error is the same as c = 0. In this case functions returns NULL
and we try another speed setting (if defined) for the terminal.
Karel
--
Karel Zak <kzak@xxxxxxxxxx>
http://karelzak.blogspot.com
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