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Use dup3() instead of dup2().

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This is less error prone since dup3() returns an error if old == new.
Sudo guarantees that fds 0-2 are already open.
This commit is contained in:
Todd C. Miller
2019-11-02 10:55:50 -06:00
parent 43df086186
commit 356287557f
4 changed files with 35 additions and 46 deletions
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19
src/selinux.c
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@@ -227,6 +227,8 @@ relabel_tty(const char *ttyn, int ptyfd)
}
if (ptyfd != -1) {
int oflags, flags = 0;
/* Reopen pty that was relabeled, std{in,out,err} are reset later. */
se_state.ttyfd = open(ttyn, O_RDWR|O_NOCTTY, 0);
if (se_state.ttyfd == -1 || fstat(se_state.ttyfd, &sb) == -1) {
@@ -238,8 +240,21 @@ relabel_tty(const char *ttyn, int ptyfd)
ttyn);
goto bad;
}
if (dup2(se_state.ttyfd, ptyfd) == -1) {
sudo_warn("dup2");
/* Preserve O_NONBLOCK and the close-on-exec flags. */
if ((oflags = fcntl(ptyfd, F_GETFL)) == -1) {
sudo_warn("F_GETFL");
goto bad;
}
if (ISSET(oflags, O_NONBLOCK))
flags |= O_NONBLOCK;
if ((oflags = fcntl(ptyfd, F_GETFD)) == -1) {
sudo_warn("F_GETFD");
goto bad;
}
if (ISSET(oflags, FD_CLOEXEC))
flags |= O_CLOEXEC;
if (dup3(se_state.ttyfd, ptyfd, flags) == -1) {
sudo_warn("dup3");
goto bad;
}
} else {