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v260
src/basic/pidref.c
545 строк
15 KB
Mike Yuan
pidref: do not tamper with pidref_acquire_pidfd_id() retval
02 мар 2026, 09:25
02 мар 2026, 09:25
a12a4bd
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/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include <poll.h> #include <sys/wait.h> #include <unistd.h> #include "alloc-util.h" #include "errno-util.h" #include "fd-util.h" #include "format-util.h" #include "hash-funcs.h" #include "io-util.h" #include "log.h" #include "parse-util.h" #include "pidfd-util.h" #include "pidref.h" #include "process-util.h" #include "siphash24.h" #include "time-util.h" int pidref_acquire_pidfd_id(PidRef *pidref) { int r; assert(pidref); if (!pidref_is_set(pidref)) return -ESRCH; if (pidref_is_remote(pidref)) return -EREMOTE; if (pidref->fd < 0) return -ENOMEDIUM; if (pidref->fd_id > 0) return 0; r = pidfd_get_inode_id(pidref->fd, &pidref->fd_id); if (r < 0) { if (!ERRNO_IS_NEG_NOT_SUPPORTED(r)) log_debug_errno(r, "Failed to get inode number of pidfd for pid " PID_FMT ": %m", pidref->pid); return r; } return 0; } bool pidref_equal(PidRef *a, PidRef *b) { /* If this is the very same structure, it definitely refers to the same process */ if (a == b) return true; if (!pidref_is_set(a)) return !pidref_is_set(b); if (!pidref_is_set(b)) return false; if (a->pid != b->pid) return false; if (pidref_is_remote(a)) { /* If one is remote and the other isn't, they are not the same */ if (!pidref_is_remote(b)) return false; /* If both are remote, compare fd IDs if we have both, otherwise don't bother, and cut things short */ if (a->fd_id == 0 || b->fd_id == 0) return true; } else { /* If the other side is remote, then this is not the same */ if (pidref_is_remote(b)) return false; /* PID1 cannot exit, hence it cannot change pidfs ids, hence no point in comparing them, we * can shortcut things */ if (a->pid == 1) return true; /* Try to compare pidfds using their inode numbers. This way we can ensure that we * don't spuriously consider two PidRefs equal if the pid has been reused once. Note * that we ignore all errors here, not only EOPNOTSUPP, as fstat() might fail due to * many reasons. */ if (pidref_acquire_pidfd_id(a) < 0 || pidref_acquire_pidfd_id(b) < 0) return true; } return a->fd_id == b->fd_id; } int pidref_set_pid(PidRef *pidref, pid_t pid) { uint64_t pidfdid = 0; int fd; assert(pidref); if (pid < 0) return -ESRCH; if (pid == 0) { pid = getpid_cached(); (void) pidfd_get_inode_id_self_cached(&pidfdid); } fd = pidfd_open(pid, 0); if (fd < 0) { /* Graceful fallback in case the kernel is out of fds */ if (!ERRNO_IS_RESOURCE(errno)) return log_debug_errno(errno, "Failed to open pidfd for pid " PID_FMT ": %m", pid); fd = -EBADF; } *pidref = (PidRef) { .fd = fd, .pid = pid, .fd_id = pidfdid, }; return 0; } int pidref_set_pid_and_pidfd_id( PidRef *pidref, pid_t pid, uint64_t pidfd_id) { int r; assert(pidref); _cleanup_(pidref_done) PidRef n = PIDREF_NULL; r = pidref_set_pid(&n, pid); if (r < 0) return r; if (pidfd_id > 0) { r = pidref_acquire_pidfd_id(&n); if (r < 0) return r; if (n.fd_id != pidfd_id) return -ESRCH; } *pidref = TAKE_PIDREF(n); return 0; } int pidref_set_pidstr(PidRef *pidref, const char *pid) { pid_t nr; int r; assert(pidref); r = parse_pid(pid, &nr); if (r < 0) return r; return pidref_set_pid(pidref, nr); } int pidref_set_pidfd(PidRef *pidref, int fd) { int r; assert(pidref); if (fd < 0) return -EBADF; int fd_copy = fcntl(fd, F_DUPFD_CLOEXEC, 3); if (fd_copy < 0) { pid_t pid; if (!ERRNO_IS_RESOURCE(errno)) return -errno; /* Graceful fallback if we are out of fds */ r = pidfd_get_pid(fd, &pid); if (r < 0) return r; *pidref = PIDREF_MAKE_FROM_PID(pid); return 0; } return pidref_set_pidfd_consume(pidref, fd_copy); } int pidref_set_pidfd_take(PidRef *pidref, int fd) { pid_t pid; int r; assert(pidref); if (fd < 0) return -EBADF; r = pidfd_get_pid(fd, &pid); if (r < 0) return r; *pidref = (PidRef) { .fd = fd, .pid = pid, }; return 0; } int pidref_set_pidfd_consume(PidRef *pidref, int fd) { int r; r = pidref_set_pidfd_take(pidref, fd); if (r < 0) safe_close(fd); return r; } int pidref_set_parent(PidRef *ret) { _cleanup_(pidref_done) PidRef parent = PIDREF_NULL; pid_t ppid; int r; assert(ret); /* Acquires a pidref to our parent process. Deals with the fact that parent processes might exit, and * we get reparented to other processes, with our old parent's PID already being recycled. */ ppid = getppid(); for (;;) { r = pidref_set_pid(&parent, ppid); if (r < 0) return r; if (parent.fd < 0) /* If pidfds are not available, then we are done */ break; pid_t now_ppid = getppid(); if (now_ppid == ppid) /* If our ppid is still the same, then we are done */ break; /* Otherwise let's try again with the new ppid */ ppid = now_ppid; pidref_done(&parent); } *ret = TAKE_PIDREF(parent); return 0; } void pidref_done(PidRef *pidref) { assert(pidref); *pidref = (PidRef) { .fd = safe_close(pidref->fd), }; } PidRef* pidref_free(PidRef *pidref) { /* Regularly, this is an embedded structure. But sometimes we want it on the heap too */ if (!pidref) return NULL; pidref_done(pidref); return mfree(pidref); } int pidref_copy(const PidRef *pidref, PidRef *ret) { _cleanup_(pidref_done) PidRef copy = PIDREF_NULL; /* If NULL is passed we'll generate a PidRef that refers to no process. This makes it easy to * copy pidref fields that might or might not reference a process yet. */ assert(ret); if (pidref) { if (pidref_is_remote(pidref)) /* Propagate remote flag */ copy.fd = -EREMOTE; else if (pidref->fd >= 0) { copy.fd = fcntl(pidref->fd, F_DUPFD_CLOEXEC, 3); if (copy.fd < 0) { if (!ERRNO_IS_RESOURCE(errno)) return -errno; copy.fd = -EBADF; } } copy.pid = pidref->pid; copy.fd_id = pidref->fd_id; } *ret = TAKE_PIDREF(copy); return 0; } int pidref_dup(const PidRef *pidref, PidRef **ret) { _cleanup_(pidref_freep) PidRef *dup_pidref = NULL; int r; /* Allocates a new PidRef on the heap, making it a copy of the specified pidref. This does not try to * acquire a pidfd if we don't have one yet! */ assert(ret); dup_pidref = newdup(PidRef, &PIDREF_NULL, 1); if (!dup_pidref) return -ENOMEM; r = pidref_copy(pidref, dup_pidref); if (r < 0) return r; *ret = TAKE_PTR(dup_pidref); return 0; } int pidref_new_from_pid(pid_t pid, PidRef **ret) { _cleanup_(pidref_freep) PidRef *n = NULL; int r; assert(ret); if (pid < 0) return -ESRCH; n = new(PidRef, 1); if (!n) return -ENOMEM; *n = PIDREF_NULL; r = pidref_set_pid(n, pid); if (r < 0) return r; *ret = TAKE_PTR(n); return 0; } int pidref_kill(const PidRef *pidref, int sig) { if (!pidref) return -ESRCH; if (pidref_is_remote(pidref)) return -EREMOTE; if (pidref->fd >= 0) return RET_NERRNO(pidfd_send_signal(pidref->fd, sig, NULL, 0)); if (pidref->pid > 0) return RET_NERRNO(kill(pidref->pid, sig)); return -ESRCH; } int pidref_kill_and_sigcont(const PidRef *pidref, int sig) { int r; r = pidref_kill(pidref, sig); if (r < 0) return r; if (!IN_SET(sig, SIGCONT, SIGKILL)) (void) pidref_kill(pidref, SIGCONT); return 0; } int pidref_sigqueue(const PidRef *pidref, int sig, int value) { if (!pidref) return -ESRCH; if (pidref_is_remote(pidref)) return -EREMOTE; if (pidref->fd >= 0) { siginfo_t si; /* We can't use structured initialization here, since the structure contains various unions * and these fields lie in overlapping (carefully aligned) unions that LLVM is allergic to * allow assignments to */ zero(si); si.si_signo = sig; si.si_code = SI_QUEUE; si.si_pid = getpid_cached(); si.si_uid = getuid(); si.si_value.sival_int = value; return RET_NERRNO(pidfd_send_signal(pidref->fd, sig, &si, 0)); } if (pidref->pid > 0) return RET_NERRNO(sigqueue(pidref->pid, sig, (const union sigval) { .sival_int = value })); return -ESRCH; } int pidref_verify(const PidRef *pidref) { int r; /* This is a helper that is supposed to be called after reading information from procfs via a * PidRef. It ensures that the PID we track still matches the PIDFD we pin. If this value differs * after a procfs read, we might have read the data from a recycled PID. */ if (!pidref_is_set(pidref)) return -ESRCH; if (pidref_is_remote(pidref)) return -EREMOTE; if (pidref->pid == 1) return 1; /* PID 1 can never go away, hence never be recycled to a different process → return 1 */ if (pidref->fd < 0) return 0; /* If we don't have a pidfd we cannot validate it, hence we assume it's all OK → return 0 */ r = pidfd_verify_pid(pidref->fd, pidref->pid); if (r < 0) return r; return 1; /* We have a pidfd and it still points to the PID we have, hence all is *really* OK → return 1 */ } bool pidref_is_self(PidRef *pidref) { if (!pidref_is_set(pidref)) return false; if (pidref_is_remote(pidref)) return false; if (pidref->pid != getpid_cached()) return false; /* PID1 cannot exit, hence no point in comparing pidfd IDs, they can never change */ if (pidref->pid == 1) return true; /* Also compare pidfd ID if we can get it */ if (pidref_acquire_pidfd_id(pidref) < 0) return true; uint64_t self_id; if (pidfd_get_inode_id_self_cached(&self_id) < 0) return true; return pidref->fd_id == self_id; } int pidref_wait_for_terminate_full(PidRef *pidref, usec_t timeout, siginfo_t *ret_si) { int r; assert(timeout > 0); if (!pidref_is_set(pidref)) return -ESRCH; if (pidref_is_remote(pidref)) return -EREMOTE; if (pidref->pid == 1 || pidref_is_self(pidref)) return -ECHILD; if (timeout != USEC_INFINITY && pidref->fd < 0) return -ENOMEDIUM; usec_t ts = timeout == USEC_INFINITY ? USEC_INFINITY : usec_add(now(CLOCK_MONOTONIC), timeout); for (;;) { if (ts != USEC_INFINITY) { usec_t left = usec_sub_unsigned(ts, now(CLOCK_MONOTONIC)); if (left == 0) return -ETIMEDOUT; r = fd_wait_for_event(pidref->fd, POLLIN, left); if (r == 0) return -ETIMEDOUT; if (r == -EINTR) continue; if (r < 0) return r; } siginfo_t si = {}; if (pidref->fd >= 0) r = RET_NERRNO(waitid(P_PIDFD, pidref->fd, &si, WEXITED)); else r = RET_NERRNO(waitid(P_PID, pidref->pid, &si, WEXITED)); if (r >= 0) { if (ret_si) *ret_si = si; return 0; } if (r != -EINTR) return r; } } bool pidref_is_automatic(const PidRef *pidref) { return pidref && pid_is_automatic(pidref->pid); } void pidref_hash_func(const PidRef *pidref, struct siphash *state) { siphash24_compress_typesafe(pidref->pid, state); } int pidref_compare_func(const PidRef *a, const PidRef *b) { int r; assert(a); assert(b); r = CMP(pidref_is_set(a), pidref_is_set(b)); if (r != 0) return r; r = CMP(pidref_is_automatic(a), pidref_is_automatic(b)); if (r != 0) return r; r = CMP(pidref_is_remote(a), pidref_is_remote(b)); if (r != 0) return r; r = CMP(a->pid, b->pid); if (r != 0) return r; if (a->fd_id != 0 && b->fd_id != 0) return CMP(a->fd_id, b->fd_id); return 0; } DEFINE_HASH_OPS(pidref_hash_ops, PidRef, pidref_hash_func, pidref_compare_func); DEFINE_HASH_OPS_WITH_KEY_DESTRUCTOR(pidref_hash_ops_free, PidRef, pidref_hash_func, pidref_compare_func, pidref_free);