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agetty: fix chown(3), chmod(3) and open(3) race 

Signed-off-by: Sami Kerola <kerolasa@iki.fi>
This commit is contained in:
Sami Kerola 2015-10-31 19:21:16 +00:00 committed by Karel Zak
parent d0a050e0f9
commit c3a9f86fcd
1 changed files with 5 additions and 5 deletions
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10
term-utils/agetty.c
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@ -1004,23 +1004,23 @@ static void open_tty(char *tty, struct termios *tp, struct options *op)
(int)sizeof(buf)) || (len < 0))
log_err(_("/dev/%s: cannot open as standard input: %m"), tty);
/* Open the tty as standard input. */
if ((fd = open(buf, O_RDWR|O_NOCTTY|O_NONBLOCK, 0)) < 0)
log_err(_("/dev/%s: cannot open as standard input: %m"), tty);
/*
* There is always a race between this reset and the call to
* vhangup() that s.o. can use to get access to your tty.
* Linux login(1) will change tty permissions. Use root owner and group
* with permission -rw------- for the period between getty and login.
*/
if (chown(buf, 0, gid) || chmod(buf, (gid ? 0620 : 0600))) {
if (fchown(fd, 0, gid) || fchmod(fd, (gid ? 0620 : 0600))) {
if (errno == EROFS)
log_warn("%s: %m", buf);
else
log_err("%s: %m", buf);
}
/* Open the tty as standard input. */
if ((fd = open(buf, O_RDWR|O_NOCTTY|O_NONBLOCK, 0)) < 0)
log_err(_("/dev/%s: cannot open as standard input: %m"), tty);
/* Sanity checks... */
if (fstat(fd, &st) < 0)
log_err("%s: %m", buf);