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terminal-util: drop support for pre-TIOCGPTPEER kernels

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Our minimum baseline is now far beyond 4.13, hence let's drop these
fallback paths.
This commit is contained in:
Lennart Poettering 2025-01-14 12:05:05 +01:00
parent 3eafa5e23c
commit 1d522f1a86
5 changed files with 5 additions and 45 deletions
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1
README
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@ -37,6 +37,7 @@ REQUIREMENTS:
≥ 4.9 for RENAME_NOREPLACE support in vfat
≥ 4.10 for cgroup-bpf egress and ingress hooks
≥ 4.11 for nsfs NS_GET_NSTYPE
≥ 4.13 for TIOCGPTPEER
≥ 4.15 for cgroup-bpf device hook and cpu controller in cgroup v2
≥ 4.17 for cgroup-bpf socket address hooks and /sys/power/resume_offset
≥ 4.20 for PSI (used by systemd-oomd)

33
src/basic/terminal-util.c
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@ -2324,7 +2324,7 @@ int terminal_is_pty_fd(int fd) {
return true;
}
int pty_open_peer_racefree(int fd, int mode) {
int pty_open_peer(int fd, int mode) {
assert(fd >= 0);
/* Opens the peer PTY using the new race-free TIOCGPTPEER ioctl() (kernel 4.13).
@ -2339,9 +2339,6 @@ int pty_open_peer_racefree(int fd, int mode) {
if (peer_fd >= 0)
return peer_fd;
if (ERRNO_IS_IOCTL_NOT_SUPPORTED(errno)) /* new ioctl() is not supported, return a clear error */
return -EOPNOTSUPP;
if (errno != EIO)
return -errno;
@ -2352,31 +2349,3 @@ int pty_open_peer_racefree(int fd, int mode) {
(void) usleep_safe(50 * USEC_PER_MSEC);
}
}
int pty_open_peer(int fd, int mode) {
int r;
assert(fd >= 0);
/* Opens the peer PTY using the new race-free TIOCGPTPEER ioctl() (kernel 4.13) if it is
* available. Otherwise falls back to the POSIX ptsname() + open() logic.
*
* Because of the fallback path this is not safe to be called on PTYs from other namespaces. (Because
* we open the peer PTY name there via a path in the file system.) */
// TODO: Remove fallback path once baseline is updated to >= 4.13, i.e. systemd v258
int peer_fd = pty_open_peer_racefree(fd, mode);
if (peer_fd >= 0)
return peer_fd;
if (!ERRNO_IS_NEG_NOT_SUPPORTED(peer_fd))
return peer_fd;
/* The racy fallback path */
_cleanup_free_ char *peer_path = NULL;
r = ptsname_malloc(fd, &peer_path);
if (r < 0)
return r;
return open_terminal(peer_path, mode);
}

1
src/basic/terminal-util.h
View File

@ -165,7 +165,6 @@ int terminal_fix_size(int input_fd, int output_fd);
int terminal_is_pty_fd(int fd);
int pty_open_peer_racefree(int fd, int mode);
int pty_open_peer(int fd, int mode);
static inline bool osc_char_is_valid(char c) {

8
src/machine/machine.c
View File

@ -805,13 +805,7 @@ int machine_start_shell(
if (!p || !utmp_id)
return log_debug_errno(SYNTHETIC_ERRNO(EINVAL), "Path of pseudo TTY has unexpected prefix");
/* First try to get an fd for the PTY peer via the new racefree ioctl(), directly. Otherwise go via
* joining the namespace, because it goes by path */
pty_fd = pty_open_peer_racefree(ptmx_fd, O_RDWR|O_NOCTTY|O_CLOEXEC);
if (ERRNO_IS_NEG_NOT_SUPPORTED(pty_fd)) {
log_debug_errno(pty_fd, "Failed to get PTY peer via racefree ioctl() (ptmx_fd=%d). Trying via joining the namespace (ptmx_name=%s): %m", ptmx_fd, ptmx_name);
pty_fd = machine_open_terminal(m, ptmx_name, O_RDWR|O_NOCTTY|O_CLOEXEC);
}
pty_fd = pty_open_peer(ptmx_fd, O_RDWR|O_NOCTTY|O_CLOEXEC);
if (pty_fd < 0)
return log_debug_errno(pty_fd, "Failed to open terminal: %m");

7
src/run/run.c
View File

@ -1964,11 +1964,8 @@ static int start_transient_service(sd_bus *bus) {
if (!pty_path)
return log_oom();
peer_fd = pty_open_peer_racefree(pty_fd, O_RDWR|O_NOCTTY|O_CLOEXEC);
if (ERRNO_IS_NEG_NOT_SUPPORTED(peer_fd))
log_debug_errno(r, "TIOCGPTPEER ioctl not available, falling back to race-ful PTY peer opening: %m");
/* We do not open the peer_fd in this case, we let systemd on the remote side open it instead */
else if (peer_fd < 0)
peer_fd = pty_open_peer(pty_fd, O_RDWR|O_NOCTTY|O_CLOEXEC);
if (peer_fd < 0)
return log_debug_errno(peer_fd, "Failed to open PTY peer: %m");
// FIXME: Introduce OpenMachinePTYEx() that accepts ownership/permission as param