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Merge pull request #34719 from poettering/pidref-remote

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pidref: add explicit concept of "remote" PidRef
This commit is contained in:
Yu Watanabe
2024-10-16 06:15:26 +09:00
committed by GitHub
parent e1efa9d804 92881e7a4f
commit 529fbd25a7
5 changed files with 160 additions and 48 deletions
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53
src/basic/pidref.c
View File

@@ -40,6 +40,9 @@ int pidref_acquire_pidfd_id(PidRef *pidref) {
if (!pidref_is_set(pidref))
return -ESRCH;
if (pidref_is_remote(pidref))
return -EREMOTE;
if (pidref->fd < 0)
return -ENOMEDIUM;
@@ -64,23 +67,36 @@ int pidref_acquire_pidfd_id(PidRef *pidref) {
bool pidref_equal(PidRef *a, PidRef *b) {
if (pidref_is_set(a)) {
if (!pidref_is_set(b))
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 (a->pid != b->pid)
/* 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 (pidref_is_remote(b))
return false;
/* 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. */
/* 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;
}
return !pidref_is_set(b);
return a->fd_id == b->fd_id;
}
int pidref_set_pid(PidRef *pidref, pid_t pid) {
@@ -240,7 +256,9 @@ int pidref_copy(const PidRef *pidref, PidRef *dest) {
assert(dest);
if (pidref) {
if (pidref->fd >= 0) {
if (pidref_is_remote(pidref)) /* Propagate remote flag */
dup_fd = -EREMOTE;
else if (pidref->fd >= 0) {
dup_fd = fcntl(pidref->fd, F_DUPFD_CLOEXEC, 3);
if (dup_fd < 0) {
if (!ERRNO_IS_RESOURCE(errno))
@@ -311,6 +329,9 @@ 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));
@@ -338,6 +359,9 @@ 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;
@@ -370,6 +394,9 @@ int pidref_verify(const PidRef *pidref) {
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 */
@@ -387,6 +414,9 @@ bool pidref_is_self(const PidRef *pidref) {
if (!pidref)
return false;
if (pidref_is_remote(pidref))
return false;
return pidref->pid == getpid_cached();
}
@@ -396,6 +426,9 @@ int pidref_wait(const PidRef *pidref, siginfo_t *ret, int options) {
if (!pidref_is_set(pidref))
return -ESRCH;
if (pidref_is_remote(pidref))
return -EREMOTE;
if (pidref->pid == 1 || pidref->pid == getpid_cached())
return -ECHILD;

37
src/basic/pidref.h
View File

@@ -6,10 +6,35 @@ typedef struct PidRef PidRef;
#include "macro.h"
#include "process-util.h"
/* An embeddable structure carrying a reference to a process. Supposed to be used when tracking processes continuously. */
/* An embeddable structure carrying a reference to a process. Supposed to be used when tracking processes
* continuously. This combines a PID, a modern Linux pidfd and the 64bit inode number of the pidfd into one
* structure. Note that depending on kernel support the pidfd might not be initialized, and if it is
* initialized then fd_id might still not be initialized (because the concept was added to the kernel much
* later than pidfds themselves).
*
* There are three special states a PidRef can be in:
*
* 1. It can be *unset*. Use pidref_is_set() to detect this case. Most operations attempted on such a PidRef
* will fail with -ESRCH. Use PIDREF_NULL for initializing a PidRef in this state.
*
* 2. It can be marked as *automatic*. This is a special state indicating that a process reference is
* supposed to be derived automatically from the current context. This is used by the Varlink/JSON
* dispatcher as indication that a PidRef shall be derived from the connection peer, but might be
* otherwise used too. When marked *automatic* the PidRef will also be considered *unset*, hence most
* operations will fail with -ESRCH, as above.
*
* 3. It can be marked as *remote*. This is useful when deserializing a PidRef structure from an IPC message
* or similar, and it has been determined that the given PID definitely doesn't refer to a local
* process. In this case the PidRef logic will refrain from trying to acquire a pidfd for the
* process. Moreover, most operations will fail with -EREMOTE. Only PidRef structures that are not marked
* *unset* can be marked *remote*.
*/
struct PidRef {
pid_t pid; /* always valid */
int fd; /* only valid if pidfd are available in the kernel, and we manage to get an fd */
pid_t pid; /* > 0 if the PidRef is set, otherwise set to PID_AUTOMATIC if automatic mode is
* desired, or 0 otherwise. */
int fd; /* only valid if pidfd are available in the kernel, and we manage to get an fd. If we
* know that the PID is not from the local machine we set this to -EREMOTE, otherwise
* we use -EBADF as indicator the fd is invalid. */
uint64_t fd_id; /* the inode number of pidfd. only useful in kernel 6.9+ where pidfds live in
their own pidfs and each process comes with a unique inode number */
};
@@ -31,6 +56,12 @@ static inline bool pidref_is_set(const PidRef *pidref) {
bool pidref_is_automatic(const PidRef *pidref);
static inline bool pidref_is_remote(const PidRef *pidref) {
/* If the fd is set to -EREMOTE we assume PidRef does not refer to a local PID, but on another
* machine (and we just got the PidRef initialized due to deserialization of some RPC message) */
return pidref_is_set(pidref) && pidref->fd == -EREMOTE;
}
int pidref_acquire_pidfd_id(PidRef *pidref);
bool pidref_equal(PidRef *a, PidRef *b);

70
src/libsystemd/sd-json/json-util.c
View File

@@ -151,7 +151,7 @@ int json_dispatch_path(const char *name, sd_json_variant *variant, sd_json_dispa
}
int json_variant_new_pidref(sd_json_variant **ret, PidRef *pidref) {
sd_id128_t boot_id;
sd_id128_t boot_id = SD_ID128_NULL;
int r;
/* Turns a PidRef into a triplet of PID, pidfd inode nr, and the boot ID. The triplet should uniquely
@@ -160,22 +160,24 @@ int json_variant_new_pidref(sd_json_variant **ret, PidRef *pidref) {
if (!pidref_is_set(pidref))
return sd_json_variant_new_null(ret);
r = pidref_acquire_pidfd_id(pidref);
if (r < 0 && !ERRNO_IS_NEG_NOT_SUPPORTED(r) && r != -ENOMEDIUM)
return r;
if (pidref->fd_id > 0) {
/* If we have the pidfd inode number, also acquire the boot ID, to make things universally unique */
r = sd_id128_get_boot(&boot_id);
if (r < 0)
if (!pidref_is_remote(pidref)) {
r = pidref_acquire_pidfd_id(pidref);
if (r < 0 && !ERRNO_IS_NEG_NOT_SUPPORTED(r) && r != -ENOMEDIUM)
return r;
/* If we have the pidfd inode number, also acquire the boot ID, to make things universally unique */
if (pidref->fd_id > 0) {
r = sd_id128_get_boot(&boot_id);
if (r < 0)
return r;
}
}
return sd_json_buildo(
ret,
SD_JSON_BUILD_PAIR_INTEGER("pid", pidref->pid),
SD_JSON_BUILD_PAIR_CONDITION(pidref->fd_id > 0, "pidfdId", SD_JSON_BUILD_INTEGER(pidref->fd_id)),
SD_JSON_BUILD_PAIR_CONDITION(pidref->fd_id > 0, "bootId", SD_JSON_BUILD_ID128(boot_id)));
SD_JSON_BUILD_PAIR_CONDITION(!sd_id128_is_null(boot_id), "bootId", SD_JSON_BUILD_ID128(boot_id)));
}
int json_dispatch_pidref(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata) {
@@ -252,7 +254,7 @@ int json_dispatch_pidref(const char *name, sd_json_variant *variant, sd_json_dis
} else {
local_boot_id = sd_id128_equal(data.boot_id, my_boot_id);
if (!local_boot_id) {
json_log(variant, flags | (FLAGS_SET(flags, SD_JSON_STRICT) ? 0 : SD_JSON_DEBUG), 0, "JSON field '%s' refers to non-local PID.", strna(name));
json_log(variant, flags | (FLAGS_SET(flags, SD_JSON_STRICT) ? 0 : SD_JSON_DEBUG), 0, "JSON field '%s' refers to non-local PID%s.", strna(name), FLAGS_SET(flags, SD_JSON_STRICT) ? "" : ", proceeding");
if (FLAGS_SET(flags, SD_JSON_STRICT))
return -ESRCH;
}
@@ -260,35 +262,41 @@ int json_dispatch_pidref(const char *name, sd_json_variant *variant, sd_json_dis
}
_cleanup_(pidref_done) PidRef np = PIDREF_NULL;
if (local_boot_id != 0) {
/* Try to acquire a pidfd – unless this is definitely not a local PID */
if (local_boot_id == 0)
/* If this is definitely not the local boot ID, then mark the PidRef as remote in the sense of pidref_is_remote() */
np = (PidRef) {
.pid = data.pid,
.fd = -EREMOTE,
.fd_id = data.fd_id,
};
else {
/* Try to acquire a pidfd if this is or might be a local PID */
r = pidref_set_pid(&np, data.pid);
if (r < 0) {
json_log(variant, flags | (FLAGS_SET(flags, SD_JSON_STRICT) ? 0 : SD_JSON_DEBUG), r, "Unable to get fd for PID in JSON field '%s': %m", strna(name));
if (FLAGS_SET(flags, SD_JSON_STRICT))
return r;
/* If the PID is dead or we otherwise can't get a pidfd of it, then store at least the PID number */
np = PIDREF_MAKE_FROM_PID(data.pid);
}
}
/* If the the PID is dead or we otherwise can't get a pidfd of it, then store at least the PID number */
if (!pidref_is_set(&np))
np = PIDREF_MAKE_FROM_PID(data.pid);
/* If the pidfd inode nr is specified, validate it or at least state */
if (data.fd_id > 0) {
if (np.fd >= 0) {
r = pidref_acquire_pidfd_id(&np);
if (r < 0 && !ERRNO_IS_NOT_SUPPORTED(r))
return json_log(variant, flags, r, "Unable to get pidfd ID to validate JSON field '%s': %m", strna(name));
/* If the pidfd inode nr is specified, validate it or at least state */
if (data.fd_id > 0) {
if (np.fd >= 0) {
r = pidref_acquire_pidfd_id(&np);
if (r < 0 && !ERRNO_IS_NOT_SUPPORTED(r))
return json_log(variant, flags, r, "Unable to get pidfd ID to validate JSON field '%s': %m", strna(name));
if (data.fd_id != np.fd_id) {
json_log(variant, flags | (FLAGS_SET(flags, SD_JSON_STRICT) ? 0 : SD_JSON_DEBUG), 0, "JSON field '%s' references PID with non-matching inode number.", strna(name));
if (FLAGS_SET(flags, SD_JSON_STRICT))
return -ESRCH;
if (data.fd_id != np.fd_id) {
json_log(variant, flags | (FLAGS_SET(flags, SD_JSON_STRICT) ? 0 : SD_JSON_DEBUG), 0, "JSON field '%s' references PID with non-matching inode number.", strna(name));
if (FLAGS_SET(flags, SD_JSON_STRICT))
return -ESRCH;
}
} else {
json_log(variant, flags|SD_JSON_DEBUG, 0, "Not validating PID inode number on JSON field '%s', because operating without pidfd.", strna(name));
np.fd_id = data.fd_id;
}
} else if (local_boot_id != 0) {
json_log(variant, flags|SD_JSON_DEBUG, 0, "Not validating PID inode number on JSON field '%s', because operating without pidfd.", strna(name));
np.fd_id = data.fd_id;
}
}

26
src/test/test-json.c
View File

@@ -1272,24 +1272,34 @@ TEST(pidref) {
assert_se(pidref_set_pid(&pid1, 1) >= 0);
_cleanup_(sd_json_variant_unrefp) sd_json_variant *v = NULL;
sd_id128_t randomized_boot_id;
assert_se(sd_id128_randomize(&randomized_boot_id) >= 0);
assert_se(sd_json_buildo(&v,
JSON_BUILD_PAIR_PIDREF("myself", &myself),
JSON_BUILD_PAIR_PIDREF("pid1", &pid1)) >= 0);
JSON_BUILD_PAIR_PIDREF("pid1", &pid1),
SD_JSON_BUILD_PAIR("remote", SD_JSON_BUILD_OBJECT(SD_JSON_BUILD_PAIR_UNSIGNED("pid", 1),
SD_JSON_BUILD_PAIR_UNSIGNED("pidfdId", 4711),
SD_JSON_BUILD_PAIR_ID128("bootId", randomized_boot_id))),
SD_JSON_BUILD_PAIR("automatic", SD_JSON_BUILD_OBJECT(SD_JSON_BUILD_PAIR_UNSIGNED("pid", 0)))) >= 0);
sd_json_variant_dump(v, SD_JSON_FORMAT_COLOR|SD_JSON_FORMAT_PRETTY, NULL, NULL);
struct {
PidRef myself, pid1;
PidRef myself, pid1, remote, automatic;
} data = {
.myself = PIDREF_NULL,
.pid1 = PIDREF_NULL,
.remote = PIDREF_NULL,
.automatic = PIDREF_NULL,
};
assert_se(sd_json_dispatch(
v,
(const sd_json_dispatch_field[]) {
{ "myself", _SD_JSON_VARIANT_TYPE_INVALID, json_dispatch_pidref, voffsetof(data, myself), 0 },
{ "pid1", _SD_JSON_VARIANT_TYPE_INVALID, json_dispatch_pidref, voffsetof(data, pid1), 0 },
{ "myself", _SD_JSON_VARIANT_TYPE_INVALID, json_dispatch_pidref, voffsetof(data, myself), SD_JSON_STRICT },
{ "pid1", _SD_JSON_VARIANT_TYPE_INVALID, json_dispatch_pidref, voffsetof(data, pid1), SD_JSON_STRICT },
{ "remote", _SD_JSON_VARIANT_TYPE_INVALID, json_dispatch_pidref, voffsetof(data, remote), 0 },
{ "automatic", _SD_JSON_VARIANT_TYPE_INVALID, json_dispatch_pidref, voffsetof(data, automatic), SD_JSON_RELAX },
{},
},
/* flags= */ 0,
@@ -1300,12 +1310,20 @@ TEST(pidref) {
assert_se(!pidref_equal(&myself, &data.pid1));
assert_se(!pidref_equal(&pid1, &data.myself));
assert_se(!pidref_equal(&myself, &data.remote));
assert_se(!pidref_equal(&pid1, &data.remote));
assert_se((myself.fd_id > 0) == (data.myself.fd_id > 0));
assert_se((pid1.fd_id > 0) == (data.pid1.fd_id > 0));
assert_se(!pidref_is_set(&data.automatic));
assert_se(pidref_is_automatic(&data.automatic));
assert_se(pidref_is_set(&data.remote));
assert_se(pidref_is_remote(&data.remote));
pidref_done(&data.myself);
pidref_done(&data.pid1);
pidref_done(&data.remote);
}
TEST(devnum) {

22
src/test/test-pidref.c
View File

@@ -240,4 +240,26 @@ TEST(pidref_is_automatic) {
assert_se(!pid_is_valid(PID_AUTOMATIC));
}
TEST(pidref_is_remote) {
assert_se(!pidref_is_remote(NULL));
assert_se(!pidref_is_remote(&PIDREF_NULL));
assert_se(!pidref_is_remote(&PIDREF_MAKE_FROM_PID(1)));
assert_se(!pidref_is_remote(&PIDREF_MAKE_FROM_PID(getpid_cached())));
assert_se(!pidref_is_remote(&PIDREF_AUTOMATIC));
static const PidRef p = {
.pid = 1,
.fd = -EREMOTE,
.fd_id = 4711,
};
assert_se(pidref_is_set(&p));
assert_se(pidref_is_remote(&p));
assert_se(!pidref_is_automatic(&p));
assert_se(pidref_kill(&p, SIGTERM) == -EREMOTE);
assert_se(pidref_kill_and_sigcont(&p, SIGTERM) == -EREMOTE);
assert_se(pidref_wait_for_terminate(&p, /* ret= */ NULL) == -EREMOTE);
assert_se(pidref_verify(&p) == -EREMOTE);
}
DEFINE_TEST_MAIN(LOG_DEBUG);