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execute: don't chown/chmod non-TTY inodes thinking they were TTYs

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Fixes: #19213

This is a safety net for invalid configurations, see the original bug
report.
This commit is contained in:
Lennart Poettering
2021-05-19 17:12:01 +02:00
parent f2df231fed
commit 0ba976e8da
1 changed files with 28 additions and 9 deletions
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src/core/execute.c
+28 -9
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@@ -5775,6 +5775,9 @@ void exec_context_free_log_extra_fields(ExecContext *c) {
}
void exec_context_revert_tty(ExecContext *c) {
_cleanup_close_ int fd = -1;
const char *path;
struct stat st;
int r;
assert(c);
@@ -5785,17 +5788,33 @@ void exec_context_revert_tty(ExecContext *c) {
/* And then undo what chown_terminal() did earlier. Note that we only do this if we have a path
* configured. If the TTY was passed to us as file descriptor we assume the TTY is opened and managed
* by whoever passed it to us and thus knows better when and how to chmod()/chown() it back. */
if (!exec_context_may_touch_tty(c))
return;
if (exec_context_may_touch_tty(c)) {
const char *path;
path = exec_context_tty_path(c);
if (!path)
return;
path = exec_context_tty_path(c);
if (path) {
r = chmod_and_chown(path, TTY_MODE, 0, TTY_GID);
if (r < 0 && r != -ENOENT)
log_warning_errno(r, "Failed to reset TTY ownership/access mode of %s, ignoring: %m", path);
}
}
fd = open(path, O_PATH|O_CLOEXEC);
if (fd < 0)
return (void) log_full_errno(errno == ENOENT ? LOG_DEBUG : LOG_WARNING, errno,
"Failed to open TTY inode of '%s' to adjust ownership/access mode, ignoring: %m",
path);
if (fstat(fd, &st) < 0)
return (void) log_warning_errno(errno, "Failed to stat TTY '%s', ignoring: %m", path);
/* Let's add a superficial check that we only do this for stuff that looks like a TTY. We only check
* if things are a character device, since a proper check either means we'd have to open the TTY and
* use isatty(), but we'd rather not do that since opening TTYs comes with all kinds of side-effects
* and is slow. Or we'd have to hardcode dev_t major information, which we'd rather avoid. Why bother
* with this at all? → https://github.com/systemd/systemd/issues/19213 */
if (!S_ISCHR(st.st_mode))
return log_warning("Configured TTY '%s' is not actually a character device, ignoring.", path);
r = fchmod_and_chown(fd, TTY_MODE, 0, TTY_GID);
if (r < 0)
log_warning_errno(r, "Failed to reset TTY ownership/access mode of %s, ignoring: %m", path);
}
int exec_context_get_clean_directories(