From de5abcb02431896a1827dff5d3376e1f2e124cd7 Mon Sep 17 00:00:00 2001 From: Jonathan Rajotte Date: Thu, 21 Jul 2022 09:30:27 -0400 Subject: [PATCH] Fix: agent port file is o+w when launching as root MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Observed issue ============== When starting as root, the following permissions are observed: [-rw-rw-rw-] agent.port [-rw-r--r--] lttng-sessiond.pid When starting as user: [-rw-rw----] agent.port [-rw-rw-r--] lttng-sessiond.pid Note that despite being created by the same function, `utils_create_pid_file`, the permissions are not the same. Cause ===== `get_wait_shm` manipulates the umask and does not restore it, thus influencing the outcome of following file creations that don't enforce specific permissions (using chmod). Also `fopen` defaults to mode `0666 & ~umask`, thus resulting in unnecessarily lax permissions when the session daemon is started as a non-privileged user (umask = 0002, most of the time). Solution ======== Mimic other call sites of umask(), modify then revert the umask. Open the pid and agent port files as 0644 letting the umask to do its job as necessary for those files. Remove unnecessary umask() usage when chmod is directly used. Known drawbacks =============== Use of umask in a multi-threaded process is not recommended. Still our current usage is limited and mostly happens during the initialization phase. The usage of umask() is required for the `wait_shm` since on FreeBSD it is not possible to chmod an shm file descriptor. The default umask would interfere here. Discussion ========== The usage in run-as is valid even when in no-clone mode (valgrind) since it is the sole user of umask() following the initialization phase. When spawned as a separate process the clearing of umask is totally valid even if it is not ideal since we are ignoring any umask set by the user. It seems like the current usage is the lesser evil here. Signed-off-by: Jonathan Rajotte Signed-off-by: Jérémie Galarneau Change-Id: Ie224d254714fff05f4bced471ebfa8f19eede26a --- src/bin/lttng-sessiond/client.cpp | 2 -- src/bin/lttng-sessiond/register.cpp | 2 -- src/common/shm.cpp | 32 +++++++++++++++-------------- src/common/utils.cpp | 28 +++++++++++++++++-------- 4 files changed, 36 insertions(+), 28 deletions(-) diff --git a/src/bin/lttng-sessiond/client.cpp b/src/bin/lttng-sessiond/client.cpp index 1f94bdad8..a52062e07 100644 --- a/src/bin/lttng-sessiond/client.cpp +++ b/src/bin/lttng-sessiond/client.cpp @@ -2396,7 +2396,6 @@ init_setup_error: static int create_client_sock(void) { int ret, client_sock; - const mode_t old_umask = umask(0); /* Create client tool unix socket */ client_sock = lttcomm_create_unix_sock( @@ -2430,7 +2429,6 @@ static int create_client_sock(void) DBG("Created client socket (fd = %i)", client_sock); ret = client_sock; end: - umask(old_umask); return ret; } diff --git a/src/bin/lttng-sessiond/register.cpp b/src/bin/lttng-sessiond/register.cpp index f6aaef623..34efeac40 100644 --- a/src/bin/lttng-sessiond/register.cpp +++ b/src/bin/lttng-sessiond/register.cpp @@ -41,7 +41,6 @@ static int create_application_socket(void) { int ret = 0; int apps_sock; - const mode_t old_umask = umask(0); /* Create the application unix socket */ apps_sock = lttcomm_create_unix_sock( @@ -74,7 +73,6 @@ static int create_application_socket(void) DBG3("Session daemon application socket created (fd = %d) ", apps_sock); ret = apps_sock; end: - umask(old_umask); return ret; error_close_socket: if (close(apps_sock)) { diff --git a/src/common/shm.cpp b/src/common/shm.cpp index e3fa9b640..300ffe357 100644 --- a/src/common/shm.cpp +++ b/src/common/shm.cpp @@ -21,8 +21,7 @@ #include "shm.hpp" /* - * Using fork to set umask in the child process (not multi-thread safe). We - * deal with the shm_open vs ftruncate race (happening when the sessiond owns + * We deal with the shm_open vs ftruncate race (happening when the sessiond owns * the shm and does not let everybody modify it, to ensure safety against * shm_unlink) by simply letting the mmap fail and retrying after a few * seconds. For global shm, everybody has rw access to it until the sessiond @@ -31,7 +30,7 @@ static int get_wait_shm(char *shm_path, size_t mmap_size, int global) { int wait_shm_fd, ret; - mode_t mode; + mode_t mode, old_mode; LTTNG_ASSERT(shm_path); @@ -51,11 +50,7 @@ static int get_wait_shm(char *shm_path, size_t mmap_size, int global) mode |= S_IROTH | S_IWOTH; } - /* - * We're alone in a child process, so we can modify the process-wide - * umask. - */ - umask(~mode); + old_mode = umask(~mode); /* * Try creating shm (or get rw access). We don't do an exclusive open, @@ -104,7 +99,7 @@ static int get_wait_shm(char *shm_path, size_t mmap_size, int global) if (ret < 0) { PERROR("Failed to truncate \"wait\" shared memory object: fd = %d, size = %zu", wait_shm_fd, mmap_size); - exit(EXIT_FAILURE); + goto error; } if (global) { @@ -112,7 +107,7 @@ static int get_wait_shm(char *shm_path, size_t mmap_size, int global) if (ret < 0) { PERROR("Failed to set ownership of \"wait\" shared memory object: fd = %d, owner = 0, group = 0", wait_shm_fd); - exit(EXIT_FAILURE); + goto error; } /* * If global session daemon, any application can @@ -124,14 +119,14 @@ static int get_wait_shm(char *shm_path, size_t mmap_size, int global) if (ret < 0) { PERROR("Failed to set the mode of the \"wait\" shared memory object: fd = %d, mode = %d", wait_shm_fd, mode); - exit(EXIT_FAILURE); + goto error; } } else { ret = fchown(wait_shm_fd, getuid(), getgid()); if (ret < 0) { PERROR("Failed to set ownership of \"wait\" shared memory object: fd = %d, owner = %d, group = %d", wait_shm_fd, getuid(), getgid()); - exit(EXIT_FAILURE); + goto error; } } @@ -139,13 +134,20 @@ static int get_wait_shm(char *shm_path, size_t mmap_size, int global) shm_path, mmap_size, global ? "true" : "false", wait_shm_fd); +end: + (void) umask(old_mode); return wait_shm_fd; error: - DBG("Failed to open shared memory file descriptor: path = '%s', mmap_size = %zu, global = %s", - shm_path, mmap_size, global ? "true" : "false"); + DBG("Failing to get the wait shm fd"); + if (wait_shm_fd >= 0) { + if (close(wait_shm_fd)) { + PERROR("Failed to close wait shm file descriptor during error handling"); + } + } - return -1; + wait_shm_fd = -1; + goto end; } /* diff --git a/src/common/utils.cpp b/src/common/utils.cpp index b4b7f749f..6c0fd261c 100644 --- a/src/common/utils.cpp +++ b/src/common/utils.cpp @@ -212,30 +212,40 @@ end: */ int utils_create_pid_file(pid_t pid, const char *filepath) { - int ret; - FILE *fp; + int ret, fd = -1; + FILE *fp = NULL; LTTNG_ASSERT(filepath); - fp = fopen(filepath, "w"); + fd = open(filepath, O_CREAT | O_WRONLY, S_IRUSR |S_IWUSR | S_IRGRP | S_IROTH); + if (fd < 0) { + PERROR("open file %s", filepath); + ret = -1; + goto error; + } + + fp = fdopen(fd, "w"); if (fp == NULL) { - PERROR("open pid file %s", filepath); + PERROR("fdopen file %s", filepath); ret = -1; + close(fd); goto error; } ret = fprintf(fp, "%d\n", (int) pid); if (ret < 0) { - PERROR("fprintf pid file"); + PERROR("fprintf file %s", filepath); + ret = -1; goto error; } - if (fclose(fp)) { - PERROR("fclose"); - } - DBG("Pid %d written in file %s", (int) pid, filepath); + DBG("'%d' written in file %s", (int) pid, filepath); ret = 0; + error: + if (fp && fclose(fp)) { + PERROR("fclose file %s", filepath); + } return ret; } -- 2.34.1