Merge pull request #15570 from poettering/cmsg-find

CMSG_FIND_DATA() and cmsg_find() work

src/basic/socket-util.c

@@ -887,7 +887,7 @@ ssize_t receive_one_fd_iov(
                 .msg_iov = iov,
                 .msg_iovlen = iovlen,
         };
-        struct cmsghdr *cmsg, *found = NULL;
+        struct cmsghdr *found;
         ssize_t k;
 
         assert(transport_fd >= 0);
@@ -905,16 +905,7 @@ ssize_t receive_one_fd_iov(
         if (k < 0)
                 return k;
 
-        CMSG_FOREACH(cmsg, &mh) {
+        found = cmsg_find(&mh, SOL_SOCKET, SCM_RIGHTS, CMSG_LEN(sizeof(int)));
-                if (cmsg->cmsg_level == SOL_SOCKET &&
-                    cmsg->cmsg_type == SCM_RIGHTS &&
-                    cmsg->cmsg_len == CMSG_LEN(sizeof(int))) {
-                        assert(!found);
-                        found = cmsg;
-                        break;
-                }
-        }
-
         if (!found) {
                 cmsg_close_all(&mh);
 

src/basic/socket-util.h

@@ -158,6 +158,14 @@ int flush_accept(int fd);
 
 struct cmsghdr* cmsg_find(struct msghdr *mh, int level, int type, socklen_t length);
 
+/* Type-safe, dereferencing version of cmsg_find() */
+#define CMSG_FIND_DATA(mh, level, type, ctype) \
+        ({                                                            \
+                struct cmsghdr *_found;                               \
+                _found = cmsg_find(mh, level, type, CMSG_LEN(sizeof(ctype))); \
+                (ctype*) (_found ? CMSG_DATA(_found) : NULL);         \
+        })
+
 /*
  * Certain hardware address types (e.g Infiniband) do not fit into sll_addr
  * (8 bytes) and run over the structure. This macro returns the correct size that

src/coredump/coredump.c

@@ -921,19 +921,11 @@ static int process_socket(int fd) {
                 /* The final zero-length datagram carries the file descriptor and tells us
                  * that we're done. */
                 if (n == 0) {
-                        struct cmsghdr *cmsg, *found = NULL;
+                        struct cmsghdr *found;
 
                         free(iovec.iov_base);
 
-                        CMSG_FOREACH(cmsg, &mh) {
+                        found = cmsg_find(&mh, SOL_SOCKET, SCM_RIGHTS, CMSG_LEN(sizeof(int)));
-                                if (cmsg->cmsg_level == SOL_SOCKET &&
-                                    cmsg->cmsg_type == SCM_RIGHTS &&
-                                    cmsg->cmsg_len == CMSG_LEN(sizeof(int))) {
-                                        assert(!found);
-                                        found = cmsg;
-                                }
-                        }
-
                         if (!found) {
                                 cmsg_close_all(&mh);
                                 r = log_error_errno(SYNTHETIC_ERRNO(EBADMSG),

src/import/importd.c

@@ -557,9 +557,8 @@ static int manager_on_notify(sd_event_source *s, int fd, uint32_t revents, void
                 .msg_control = &control,
                 .msg_controllen = sizeof(control),
         };
-        struct ucred *ucred = NULL;
+        struct ucred *ucred;
         Manager *m = userdata;
-        struct cmsghdr *cmsg;
         char *p, *e;
         Transfer *t;
         Iterator i;
@@ -574,17 +573,12 @@ static int manager_on_notify(sd_event_source *s, int fd, uint32_t revents, void
 
         cmsg_close_all(&msghdr);
 
-        CMSG_FOREACH(cmsg, &msghdr)
-                if (cmsg->cmsg_level == SOL_SOCKET &&
-                    cmsg->cmsg_type == SCM_CREDENTIALS &&
-                    cmsg->cmsg_len == CMSG_LEN(sizeof(struct ucred)))
-                        ucred = (struct ucred*) CMSG_DATA(cmsg);
-
         if (msghdr.msg_flags & MSG_TRUNC) {
                 log_warning("Got overly long notification datagram, ignoring.");
                 return 0;
         }
 
+        ucred = CMSG_FIND_DATA(&msghdr, SOL_SOCKET, SCM_CREDENTIALS, struct ucred);
         if (!ucred || ucred->pid <= 0) {
                 log_warning("Got notification datagram lacking credential information, ignoring.");
                 return 0;

src/journal/journald-stream.c

@@ -491,8 +491,7 @@ static int stdout_stream_scan(StdoutStream *s, bool force_flush) {
 static int stdout_stream_process(sd_event_source *es, int fd, uint32_t revents, void *userdata) {
         uint8_t buf[CMSG_SPACE(sizeof(struct ucred))];
         StdoutStream *s = userdata;
-        struct ucred *ucred = NULL;
+        struct ucred *ucred;
-        struct cmsghdr *cmsg;
         struct iovec iovec;
         size_t limit;
         ssize_t l;
@@ -541,25 +540,14 @@ static int stdout_stream_process(sd_event_source *es, int fd, uint32_t revents,
                 goto terminate;
         }
 
-        CMSG_FOREACH(cmsg, &msghdr)
+        /* Invalidate the context if the pid of the sender changed.  This happens when a forked process
-                if (cmsg->cmsg_level == SOL_SOCKET &&
+         * inherits stdout / stderr from a parent. In this case getpeercred returns the ucred of the parent,
-                    cmsg->cmsg_type == SCM_CREDENTIALS &&
+         * which can be invalid if the parent has exited in the meantime.
-                    cmsg->cmsg_len == CMSG_LEN(sizeof(struct ucred))) {
-                        assert(!ucred);
-                        ucred = (struct ucred *)CMSG_DATA(cmsg);
-                        break;
-                }
-
-        /* Invalidate the context if the pid of the sender changed.
-         * This happens when a forked process inherits stdout / stderr
-         * from a parent. In this case getpeercred returns the ucred
-         * of the parent, which can be invalid if the parent has exited
-         * in the meantime.
          */
+        ucred = CMSG_FIND_DATA(&msghdr, SOL_SOCKET, SCM_CREDENTIALS, struct ucred);
         if (ucred && ucred->pid != s->ucred.pid) {
-                /* force out any previously half-written lines from a
+                /* force out any previously half-written lines from a different process, before we switch to
-                 * different process, before we switch to the new ucred
+                 * the new ucred structure for everything we just added */
-                 * structure for everything we just added */
                 r = stdout_stream_scan(s, true);
                 if (r < 0)
                         goto terminate;

src/libsystemd-network/sd-dhcp-client.c

@@ -1937,14 +1937,10 @@ static int client_receive_message_raw(
         if ((size_t) len < sizeof(DHCPPacket))
                 return 0;
 
-        CMSG_FOREACH(cmsg, &msg)
+        cmsg = cmsg_find(&msg, SOL_PACKET, PACKET_AUXDATA, CMSG_LEN(sizeof(struct tpacket_auxdata)));
-                if (cmsg->cmsg_level == SOL_PACKET &&
+        if (cmsg) {
-                    cmsg->cmsg_type == PACKET_AUXDATA &&
-                    cmsg->cmsg_len == CMSG_LEN(sizeof(struct tpacket_auxdata))) {
                 struct tpacket_auxdata *aux = (struct tpacket_auxdata*) CMSG_DATA(cmsg);
-
                 checksum = !(aux->tp_status & TP_STATUS_CSUMNOTREADY);
-                        break;
         }
 
         r = dhcp_packet_verify_headers(packet, len, checksum, client->port);

src/libsystemd/sd-netlink/netlink-socket.c

@@ -238,7 +238,7 @@ int socket_write_message(sd_netlink *nl, sd_netlink_message *m) {
         return k;
 }
 
-static int socket_recv_message(int fd, struct iovec *iov, uint32_t *_group, bool peek) {
+static int socket_recv_message(int fd, struct iovec *iov, uint32_t *ret_mcast_group, bool peek) {
         union sockaddr_union sender;
         uint8_t cmsg_buffer[CMSG_SPACE(sizeof(struct nl_pktinfo))];
         struct msghdr msg = {
@@ -249,8 +249,6 @@ static int socket_recv_message(int fd, struct iovec *iov, uint32_t *_group, bool
                 .msg_control = cmsg_buffer,
                 .msg_controllen = sizeof(cmsg_buffer),
         };
-        struct cmsghdr *cmsg;
-        uint32_t group = 0;
         ssize_t n;
 
         assert(fd >= 0);
@@ -281,19 +279,15 @@ static int socket_recv_message(int fd, struct iovec *iov, uint32_t *_group, bool
                 return 0;
         }
 
-        CMSG_FOREACH(cmsg, &msg) {
+        if (ret_mcast_group) {
-                if (cmsg->cmsg_level == SOL_NETLINK &&
+                struct cmsghdr *cmsg;
-                    cmsg->cmsg_type == NETLINK_PKTINFO &&
-                    cmsg->cmsg_len == CMSG_LEN(sizeof(struct nl_pktinfo))) {
-                        struct nl_pktinfo *pktinfo = (void *)CMSG_DATA(cmsg);
 
-                        /* multi-cast group */
+                cmsg = cmsg_find(&msg, SOL_NETLINK, NETLINK_PKTINFO, CMSG_LEN(sizeof(struct nl_pktinfo)));
-                        group = pktinfo->group;
+                if (ret_mcast_group)
+                        *ret_mcast_group = ((struct nl_pktinfo*) CMSG_DATA(cmsg))->group;
+                else
+                        *ret_mcast_group = 0;
         }
-        }
-
-        if (_group)
-                *_group = group;
 
         return (int) n;
 }

src/nspawn/nspawn.c

@@ -3698,8 +3698,7 @@ static int nspawn_dispatch_notify_fd(sd_event_source *source, int fd, uint32_t r
                 .msg_control = &control,
                 .msg_controllen = sizeof(control),
         };
-        struct cmsghdr *cmsg;
+        struct ucred *ucred;
-        struct ucred *ucred = NULL;
         ssize_t n;
         pid_t inner_child_pid;
         _cleanup_strv_free_ char **tags = NULL;
@@ -3721,15 +3720,7 @@ static int nspawn_dispatch_notify_fd(sd_event_source *source, int fd, uint32_t r
 
         cmsg_close_all(&msghdr);
 
-        CMSG_FOREACH(cmsg, &msghdr) {
+        ucred = CMSG_FIND_DATA(&msghdr, SOL_SOCKET, SCM_CREDENTIALS, struct ucred);
-                if (cmsg->cmsg_level == SOL_SOCKET &&
-                           cmsg->cmsg_type == SCM_CREDENTIALS &&
-                           cmsg->cmsg_len == CMSG_LEN(sizeof(struct ucred))) {
-
-                        ucred = (struct ucred*) CMSG_DATA(cmsg);
-                }
-        }
-
         if (!ucred || ucred->pid != inner_child_pid) {
                 log_debug("Received notify message without valid credentials. Ignoring.");
                 return 0;

src/shared/ask-password-api.c

@@ -940,15 +940,12 @@ int ask_password_agent(
                         continue;
                 }
 
-                if (msghdr.msg_controllen < CMSG_LEN(sizeof(struct ucred)) ||
+                ucred = CMSG_FIND_DATA(&msghdr, SOL_SOCKET, SCM_CREDENTIALS, struct ucred);
-                    control.cmsghdr.cmsg_level != SOL_SOCKET ||
+                if (!ucred) {
-                    control.cmsghdr.cmsg_type != SCM_CREDENTIALS ||
-                    control.cmsghdr.cmsg_len != CMSG_LEN(sizeof(struct ucred))) {
                         log_debug("Received message without credentials. Ignoring.");
                         continue;
                 }
 
-                ucred = (struct ucred*) CMSG_DATA(&control.cmsghdr);
                 if (ucred->uid != 0) {
                         log_debug("Got request from unprivileged user. Ignoring.");
                         continue;

src/udev/udevd.c

@@ -916,9 +916,8 @@ static int on_worker(sd_event_source *s, int fd, uint32_t revents, void *userdat
                         .msg_control = &control,
                         .msg_controllen = sizeof(control),
                 };
-                struct cmsghdr *cmsg;
                 ssize_t size;
-                struct ucred *ucred = NULL;
+                struct ucred *ucred;
                 struct worker *worker;
 
                 size = recvmsg_safe(fd, &msghdr, MSG_DONTWAIT);
@@ -937,12 +936,7 @@ static int on_worker(sd_event_source *s, int fd, uint32_t revents, void *userdat
                         continue;
                 }
 
-                CMSG_FOREACH(cmsg, &msghdr)
+                ucred = CMSG_FIND_DATA(&msghdr, SOL_SOCKET, SCM_CREDENTIALS, struct ucred);
-                        if (cmsg->cmsg_level == SOL_SOCKET &&
-                            cmsg->cmsg_type == SCM_CREDENTIALS &&
-                            cmsg->cmsg_len == CMSG_LEN(sizeof(struct ucred)))
-                                ucred = (struct ucred*) CMSG_DATA(cmsg);
-
                 if (!ucred || ucred->pid <= 0) {
                         log_warning("Ignoring worker message without valid PID");
                         continue;