From 53fabd4b86e15869e13fb762686d674c64294385 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Thu, 16 Mar 2017 16:29:45 +0100 Subject: [PATCH] qemu-ga: obey LISTEN_PID when using systemd socket activation qemu-ga's socket activation support was not obeying the LISTEN_PID environment variable, which avoids that a process uses a socket-activation file descriptor meant for its parent. Mess can for example ensue if a process forks a children before consuming the socket-activation file descriptor and therefore setting O_CLOEXEC on it. Luckily, qemu-nbd also got socket activation code, and its copy does support LISTEN_PID. Some extra fixups are needed to ensure that the code can be used for both, but that's what this patch does. The main change is to replace get_listen_fds's "consume" argument with the FIRST_SOCKET_ACTIVATION_FD macro from the qemu-nbd code. Cc: "Richard W.M. Jones" Cc: Stefan Hajnoczi Reviewed-by: Daniel P. Berrange Signed-off-by: Paolo Bonzini --- include/qemu/systemd.h | 26 +++++++++++ qemu-nbd.c | 100 ++++------------------------------------- qga/main.c | 51 ++++++--------------- util/Makefile.objs | 1 + util/systemd.c | 77 +++++++++++++++++++++++++++++++ 5 files changed, 125 insertions(+), 130 deletions(-) create mode 100644 include/qemu/systemd.h create mode 100644 util/systemd.c diff --git a/include/qemu/systemd.h b/include/qemu/systemd.h new file mode 100644 index 0000000000..e6a877e5c6 --- /dev/null +++ b/include/qemu/systemd.h @@ -0,0 +1,26 @@ +/* + * systemd socket activation support + * + * Copyright 2017 Red Hat, Inc. and/or its affiliates + * + * Authors: + * Richard W.M. Jones + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + +#ifndef QEMU_SYSTEMD_H +#define QEMU_SYSTEMD_H 1 + +#define FIRST_SOCKET_ACTIVATION_FD 3 /* defined by systemd ABI */ + +/* + * Check if socket activation was requested via use of the + * LISTEN_FDS and LISTEN_PID environment variables. + * + * Returns 0 if no socket activation, or the number of FDs. + */ +unsigned int check_socket_activation(void); + +#endif diff --git a/qemu-nbd.c b/qemu-nbd.c index e4fede641e..e080fb7c75 100644 --- a/qemu-nbd.c +++ b/qemu-nbd.c @@ -28,6 +28,7 @@ #include "qemu/config-file.h" #include "qemu/bswap.h" #include "qemu/log.h" +#include "qemu/systemd.h" #include "block/snapshot.h" #include "qapi/util.h" #include "qapi/qmp/qstring.h" @@ -474,98 +475,6 @@ static void setup_address_and_port(const char **address, const char **port) } } -#define FIRST_SOCKET_ACTIVATION_FD 3 /* defined by systemd ABI */ - -#ifndef _WIN32 -/* - * Check if socket activation was requested via use of the - * LISTEN_FDS and LISTEN_PID environment variables. - * - * Returns 0 if no socket activation, or the number of FDs. - */ -static unsigned int check_socket_activation(void) -{ - const char *s; - unsigned long pid; - unsigned long nr_fds; - unsigned int i; - int fd; - int err; - - s = getenv("LISTEN_PID"); - if (s == NULL) { - return 0; - } - err = qemu_strtoul(s, NULL, 10, &pid); - if (err) { - if (verbose) { - fprintf(stderr, "malformed %s environment variable (ignored)\n", - "LISTEN_PID"); - } - return 0; - } - if (pid != getpid()) { - if (verbose) { - fprintf(stderr, "%s was not for us (ignored)\n", - "LISTEN_PID"); - } - return 0; - } - - s = getenv("LISTEN_FDS"); - if (s == NULL) { - return 0; - } - err = qemu_strtoul(s, NULL, 10, &nr_fds); - if (err) { - if (verbose) { - fprintf(stderr, "malformed %s environment variable (ignored)\n", - "LISTEN_FDS"); - } - return 0; - } - assert(nr_fds <= UINT_MAX); - - /* A limitation of current qemu-nbd is that it can only listen on - * a single socket. When that limitation is lifted, we can change - * this function to allow LISTEN_FDS > 1, and remove the assertion - * in the main function below. - */ - if (nr_fds > 1) { - error_report("qemu-nbd does not support socket activation with %s > 1", - "LISTEN_FDS"); - exit(EXIT_FAILURE); - } - - /* So these are not passed to any child processes we might start. */ - unsetenv("LISTEN_FDS"); - unsetenv("LISTEN_PID"); - - /* So the file descriptors don't leak into child processes. */ - for (i = 0; i < nr_fds; ++i) { - fd = FIRST_SOCKET_ACTIVATION_FD + i; - if (fcntl(fd, F_SETFD, FD_CLOEXEC) == -1) { - /* If we cannot set FD_CLOEXEC then it probably means the file - * descriptor is invalid, so socket activation has gone wrong - * and we should exit. - */ - error_report("Socket activation failed: " - "invalid file descriptor fd = %d: %m", - fd); - exit(EXIT_FAILURE); - } - } - - return (unsigned int) nr_fds; -} - -#else /* !_WIN32 */ -static unsigned int check_socket_activation(void) -{ - return 0; -} -#endif - /* * Check socket parameters compatibility when socket activation is used. */ @@ -892,6 +801,13 @@ int main(int argc, char **argv) error_report("%s", err_msg); exit(EXIT_FAILURE); } + + /* qemu-nbd can only listen on a single socket. */ + if (socket_activation > 1) { + error_report("qemu-nbd does not support socket activation with %s > 1", + "LISTEN_FDS"); + exit(EXIT_FAILURE); + } } if (tlscredsid) { diff --git a/qga/main.c b/qga/main.c index 92658bc0e2..07c295376f 100644 --- a/qga/main.c +++ b/qga/main.c @@ -29,6 +29,7 @@ #include "qemu/bswap.h" #include "qemu/help_option.h" #include "qemu/sockets.h" +#include "qemu/systemd.h" #ifdef _WIN32 #include "qga/service-win32.h" #include "qga/vss-win32.h" @@ -186,37 +187,6 @@ void reopen_fd_to_null(int fd) } #endif -/** - * get_listen_fd: - * @consume: true to prevent future calls from succeeding - * - * Fetch a listen file descriptor that was passed via systemd socket - * activation. Use @consume to prevent child processes from thinking a file - * descriptor was passed. - * - * Returns: file descriptor or -1 if no fd was passed - */ -static int get_listen_fd(bool consume) -{ -#ifdef _WIN32 - return -1; /* no fd passing expected, unsetenv(3) not available */ -#else - const char *listen_fds = getenv("LISTEN_FDS"); - int fd = STDERR_FILENO + 1; - - if (!listen_fds || strcmp(listen_fds, "1") != 0) { - return -1; - } - - if (consume) { - unsetenv("LISTEN_FDS"); - } - - qemu_set_cloexec(fd); - return fd; -#endif /* !_WIN32 */ -} - static void usage(const char *cmd) { printf( @@ -1251,7 +1221,7 @@ static bool check_is_frozen(GAState *s) return false; } -static int run_agent(GAState *s, GAConfig *config) +static int run_agent(GAState *s, GAConfig *config, int socket_activation) { ga_state = s; @@ -1333,7 +1303,7 @@ static int run_agent(GAState *s, GAConfig *config) s->main_loop = g_main_loop_new(NULL, false); if (!channel_init(ga_state, config->method, config->channel_path, - get_listen_fd(true))) { + socket_activation ? FIRST_SOCKET_ACTIVATION_FD : -1)) { g_critical("failed to initialize guest agent channel"); return EXIT_FAILURE; } @@ -1357,7 +1327,7 @@ int main(int argc, char **argv) int ret = EXIT_SUCCESS; GAState *s = g_new0(GAState, 1); GAConfig *config = g_new0(GAConfig, 1); - int listen_fd; + int socket_activation; config->log_level = G_LOG_LEVEL_ERROR | G_LOG_LEVEL_CRITICAL; @@ -1379,8 +1349,13 @@ int main(int argc, char **argv) config->method = g_strdup("virtio-serial"); } - listen_fd = get_listen_fd(false); - if (listen_fd >= 0) { + socket_activation = check_socket_activation(); + if (socket_activation > 1) { + g_critical("qemu-ga only supports listening on one socket"); + ret = EXIT_FAILURE; + goto end; + } + if (socket_activation) { SocketAddress *addr; g_free(config->method); @@ -1388,7 +1363,7 @@ int main(int argc, char **argv) config->method = NULL; config->channel_path = NULL; - addr = socket_local_address(listen_fd, NULL); + addr = socket_local_address(FIRST_SOCKET_ACTIVATION_FD, NULL); if (addr) { if (addr->type == SOCKET_ADDRESS_KIND_UNIX) { config->method = g_strdup("unix-listen"); @@ -1433,7 +1408,7 @@ int main(int argc, char **argv) goto end; } - ret = run_agent(s, config); + ret = run_agent(s, config, socket_activation); end: if (s->command_state) { diff --git a/util/Makefile.objs b/util/Makefile.objs index 06366b5828..c6205ebf86 100644 --- a/util/Makefile.objs +++ b/util/Makefile.objs @@ -42,3 +42,4 @@ util-obj-y += log.o util-obj-y += qdist.o util-obj-y += qht.o util-obj-y += range.o +util-obj-y += systemd.o diff --git a/util/systemd.c b/util/systemd.c new file mode 100644 index 0000000000..d22e86c707 --- /dev/null +++ b/util/systemd.c @@ -0,0 +1,77 @@ +/* + * systemd socket activation support + * + * Copyright 2017 Red Hat, Inc. and/or its affiliates + * + * Authors: + * Richard W.M. Jones + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + +#include "qemu/osdep.h" +#include "qemu/systemd.h" +#include "qemu/cutils.h" +#include "qemu/error-report.h" + +#ifndef _WIN32 +unsigned int check_socket_activation(void) +{ + const char *s; + unsigned long pid; + unsigned long nr_fds; + unsigned int i; + int fd; + int err; + + s = getenv("LISTEN_PID"); + if (s == NULL) { + return 0; + } + err = qemu_strtoul(s, NULL, 10, &pid); + if (err) { + return 0; + } + if (pid != getpid()) { + return 0; + } + + s = getenv("LISTEN_FDS"); + if (s == NULL) { + return 0; + } + err = qemu_strtoul(s, NULL, 10, &nr_fds); + if (err) { + return 0; + } + assert(nr_fds <= UINT_MAX); + + /* So these are not passed to any child processes we might start. */ + unsetenv("LISTEN_FDS"); + unsetenv("LISTEN_PID"); + + /* So the file descriptors don't leak into child processes. */ + for (i = 0; i < nr_fds; ++i) { + fd = FIRST_SOCKET_ACTIVATION_FD + i; + if (fcntl(fd, F_SETFD, FD_CLOEXEC) == -1) { + /* If we cannot set FD_CLOEXEC then it probably means the file + * descriptor is invalid, so socket activation has gone wrong + * and we should exit. + */ + error_report("Socket activation failed: " + "invalid file descriptor fd = %d: %m", + fd); + exit(EXIT_FAILURE); + } + } + + return (unsigned int) nr_fds; +} + +#else /* !_WIN32 */ +unsigned int check_socket_activation(void) +{ + return 0; +} +#endif