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- From 10e8001ad876d8cb3b5a17c7492e713bbc047975 Mon Sep 17 00:00:00 2001
- From: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
- Date: Thu, 28 Mar 2019 18:31:29 -0400
- Subject: [PATCH] Fix: getgrnam is not MT-Safe, use getgrnam_r
-
- Running the test suite under a Yocto musl build resulted in musl
- coredump due to double freeing.
-
- We get the following backtraces:
-
- 0 a_crash () at ./arch/x86_64/atomic_arch.h:108
- 1 unmap_chunk (self=<optimized out>) at src/malloc/malloc.c:515
- 2 free (p=<optimized out>) at src/malloc/malloc.c:526
- 3 0x00007f46d9dc3849 in __getgrent_a (f=f@entry=0x7f46d9d1f7e0, gr=gr@entry=0x7f46d9e24460 <gr>, line=line@entry=0x7f46d9e26058 <line>, size=size@entry=0x7f46d92db550, mem=mem@entry=0x7f46d9e26050 <mem>, nmem=nmem@entry=0x7f46d92db558, res=0x7f46d92db548) at src/passwd/getgrent_a.c:45
- 4 0x00007f46d9dc2e6b in __getgr_a (name=0x487242 "tracing", gid=gid@entry=0, gr=gr@entry=0x7f46d9e24460 <gr>, buf=buf@entry=0x7f46d9e26058 <line>, size=size@entry=0x7f46d92db550, mem=mem@entry=0x7f46d9e26050 <mem>, nmem=0x7f46d92db558, res=0x7f46d92db548) at src/passwd/getgr_a.c:30
- 5 0x00007f46d9dc3733 in getgrnam (name=<optimized out>) at src/passwd/getgrent.c:37
- 6 0x0000000000460b29 in utils_get_group_id (name=<optimized out>) at ../../../lttng-tools-2.10.6/src/common/utils.c:1241
- 7 0x000000000044ee69 in thread_manage_health (data=<optimized out>) at ../../../../lttng-tools-2.10.6/src/bin/lttng-sessiond/main.c:4115
- 8 0x00007f46d9de1541 in start (p=<optimized out>) at src/thread/pthread_create.c:195
- 9 0x00007f46d9dee661 in __clone () at src/thread/x86_64/clone.s:22
-
- From another run:
-
- 0 a_crash () at ./arch/x86_64/atomic_arch.h:108
- 1 unmap_chunk (self=<optimized out>) at src/malloc/malloc.c:515
- 2 free (p=<optimized out>) at src/malloc/malloc.c:526
- 3 0x00007f5abc210849 in __getgrent_a (f=f@entry=0x7f5abc2733e0, gr=gr@entry=0x7f5abc271460 <gr>, line=line@entry=0x7f5abc273058 <line>, size=size@entry=0x7f5abaef5510, mem=mem@entry=0x7f5abc273050 <mem>, nmem=nmem@entry=0x7f5abaef5518, res=0x7f5abaef5508) at src/passwd/getgrent_a.c:45
- 4 0x00007f5abc20fe6b in __getgr_a (name=0x487242 "tracing", gid=gid@entry=0, gr=gr@entry=0x7f5abc271460 <gr>, buf=buf@entry=0x7f5abc273058 <line>, size=size@entry=0x7f5abaef5510, mem=mem@entry=0x7f5abc273050 <mem>, nmem=0x7f5abaef5518, res=0x7f5abaef5508) at src/passwd/getgr_a.c:30
- 5 0x00007f5abc210733 in getgrnam (name=<optimized out>) at src/passwd/getgrent.c:37
- 6 0x0000000000460b29 in utils_get_group_id (name=<optimized out>) at ../../../lttng-tools-2.10.6/src/common/utils.c:1241
- 7 0x000000000042dee4 in notification_channel_socket_create () at ../../../../lttng-tools-2.10.6/src/bin/lttng-sessiond/notification-thread.c:238
- 8 init_thread_state (state=0x7f5abaef5560, handle=0x7f5abbf9be40) at ../../../../lttng-tools-2.10.6/src/bin/lttng-sessiond/notification-thread.c:375
- 9 thread_notification (data=0x7f5abbf9be40) at ../../../../lttng-tools-2.10.6/src/bin/lttng-sessiond/notification-thread.c:495
- 10 0x00007f5abc22e541 in start (p=<optimized out>) at src/thread/pthread_create.c:195
- 11 0x00007f5abc23b661 in __clone () at src/thread/x86_64/clone.s:22
-
- The problem was easily reproducible (~6 crash on ~300 runs). A prototype fix
- using mutex around the getgrnam yielded no crash in over 1000 runs. This
- patch yielded the same results as the prototype fix.
-
- Unfortunately we cannot rely on a mutex in liblttng-ctl since we cannot
- enforce the locking for the application using the lib.
-
- Use getgrnam_r instead.
-
- The previous implementation of utils_get_group_id returned the gid of
- the root group (0) on error/not found. lttng_check_tracing_group needs
- to know if an error/not found occured, returning the root group is not
- enough. We now return the gid via the passed parameter. The caller is
- responsible for either defaulting to the root group or propagating the
- error.
-
- We also do not want to warn when used in liblttng-ctl context. We might
- want to move the warning elsewhere in the future. For now, pass a bool
- if we need to warn or not.
-
- Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
- ---
- src/bin/lttng-consumerd/health-consumerd.c | 10 ++-
- src/bin/lttng-relayd/health-relayd.c | 20 ++++--
- src/bin/lttng-sessiond/main.c | 24 +++++--
- src/bin/lttng-sessiond/notification-thread.c | 10 ++-
- src/common/utils.c | 75 +++++++++++++++++---
- src/common/utils.h | 4 +-
- src/lib/lttng-ctl/lttng-ctl.c | 8 +--
- 7 files changed, 122 insertions(+), 29 deletions(-)
-
- diff --git a/src/bin/lttng-consumerd/health-consumerd.c b/src/bin/lttng-consumerd/health-consumerd.c
- index 1e2f31e4..6045401a 100644
- --- a/src/bin/lttng-consumerd/health-consumerd.c
- +++ b/src/bin/lttng-consumerd/health-consumerd.c
- @@ -184,8 +184,14 @@ void *thread_manage_health(void *data)
- is_root = !getuid();
- if (is_root) {
- /* lttng health client socket path permissions */
- - ret = chown(health_unix_sock_path, 0,
- - utils_get_group_id(tracing_group_name));
- + gid_t gid;
- +
- + ret = utils_get_group_id(tracing_group_name, true, &gid);
- + if (ret) {
- + gid = 0; /* Default to root group. */
- + }
- +
- + ret = chown(health_unix_sock_path, 0, gid);
- if (ret < 0) {
- ERR("Unable to set group on %s", health_unix_sock_path);
- PERROR("chown");
- diff --git a/src/bin/lttng-relayd/health-relayd.c b/src/bin/lttng-relayd/health-relayd.c
- index ba996621..962e88c4 100644
- --- a/src/bin/lttng-relayd/health-relayd.c
- +++ b/src/bin/lttng-relayd/health-relayd.c
- @@ -105,8 +105,14 @@ static int create_lttng_rundir_with_perm(const char *rundir)
- int is_root = !getuid();
-
- if (is_root) {
- - ret = chown(rundir, 0,
- - utils_get_group_id(tracing_group_name));
- + gid_t gid;
- +
- + ret = utils_get_group_id(tracing_group_name, true, &gid);
- + if (ret) {
- + gid = 0; /* Default to root group.*/
- + }
- +
- + ret = chown(rundir, 0, gid);
- if (ret < 0) {
- ERR("Unable to set group on %s", rundir);
- PERROR("chown");
- @@ -256,8 +262,14 @@ void *thread_manage_health(void *data)
- is_root = !getuid();
- if (is_root) {
- /* lttng health client socket path permissions */
- - ret = chown(health_unix_sock_path, 0,
- - utils_get_group_id(tracing_group_name));
- + gid_t gid;
- +
- + ret = utils_get_group_id(tracing_group_name, true, &gid);
- + if (ret) {
- + gid = 0; /* Default to root group */
- + }
- +
- + ret = chown(health_unix_sock_path, 0, gid);
- if (ret < 0) {
- ERR("Unable to set group on %s", health_unix_sock_path);
- PERROR("chown");
- diff --git a/src/bin/lttng-sessiond/main.c b/src/bin/lttng-sessiond/main.c
- index fa6fa483..49307064 100644
- --- a/src/bin/lttng-sessiond/main.c
- +++ b/src/bin/lttng-sessiond/main.c
- @@ -4112,8 +4112,14 @@ static void *thread_manage_health(void *data)
-
- if (is_root) {
- /* lttng health client socket path permissions */
- - ret = chown(config.health_unix_sock_path.value, 0,
- - utils_get_group_id(config.tracing_group_name.value));
- + gid_t gid;
- +
- + ret = utils_get_group_id(config.tracing_group_name.value, true, &gid);
- + if (ret) {
- + gid = 0; /* Default to root group */
- + }
- +
- + ret = chown(config.health_unix_sock_path.value, 0, &gid);
- if (ret < 0) {
- ERR("Unable to set group on %s", config.health_unix_sock_path.value);
- PERROR("chown");
- @@ -5238,7 +5244,10 @@ static int set_permissions(char *rundir)
- int ret;
- gid_t gid;
-
- - gid = utils_get_group_id(config.tracing_group_name.value);
- + ret = utils_get_group_id(config.tracing_group_name.value, true, &gid);
- + if (ret) {
- + gid = 0; /* Default to root group */
- + }
-
- /* Set lttng run dir */
- ret = chown(rundir, 0, gid);
- @@ -5349,7 +5358,14 @@ static int set_consumer_sockets(struct consumer_data *consumer_data)
- goto error;
- }
- if (is_root) {
- - ret = chown(path, 0, utils_get_group_id(config.tracing_group_name.value));
- + gid_t gid;
- +
- + ret = utils_get_group_id(config.tracing_group_name.value, true, &gid);
- + if (ret) {
- + gid = 0; /* Default to root group */
- + }
- +
- + ret = chown(path, 0, gid);
- if (ret < 0) {
- ERR("Unable to set group on %s", path);
- PERROR("chown");
- diff --git a/src/bin/lttng-sessiond/notification-thread.c b/src/bin/lttng-sessiond/notification-thread.c
- index 92ac597f..18a264d9 100644
- --- a/src/bin/lttng-sessiond/notification-thread.c
- +++ b/src/bin/lttng-sessiond/notification-thread.c
- @@ -235,8 +235,14 @@ int notification_channel_socket_create(void)
- }
-
- if (getuid() == 0) {
- - ret = chown(sock_path, 0,
- - utils_get_group_id(config.tracing_group_name.value));
- + gid_t gid;
- +
- + ret = utils_get_group_id(config.tracing_group_name.value, true, &gid);
- + if (ret) {
- + gid = 0; /* Default to root group. */
- + }
- +
- + ret = chown(sock_path, 0, gid);
- if (ret) {
- ERR("Failed to set the notification channel socket's group");
- ret = -1;
- diff --git a/src/common/utils.c b/src/common/utils.c
- index c0bb031e..778bc00f 100644
- --- a/src/common/utils.c
- +++ b/src/common/utils.c
- @@ -1231,24 +1231,77 @@ size_t utils_get_current_time_str(const char *format, char *dst, size_t len)
- }
-
- /*
- - * Return the group ID matching name, else 0 if it cannot be found.
- + * Return 0 on success and set *gid to the group_ID matching the passed name.
- + * Else -1 if it cannot be found or an error occurred.
- */
- LTTNG_HIDDEN
- -gid_t utils_get_group_id(const char *name)
- +int utils_get_group_id(const char *name, bool warn, gid_t *gid)
- {
- - struct group *grp;
- + static volatile int warn_once;
-
- - grp = getgrnam(name);
- - if (!grp) {
- - static volatile int warn_once;
- + int ret;
- + long sys_len;
- + size_t len;
- + struct group grp;
- + struct group *result;
- + char *buffer = NULL;
-
- - if (!warn_once) {
- - WARN("No tracing group detected");
- - warn_once = 1;
- + /* Get the system limit if it exists */
- + sys_len = sysconf(_SC_GETGR_R_SIZE_MAX);
- + if (sys_len == -1) {
- + len = 1024;
- + } else {
- + len = (size_t) sys_len;
- + }
- +
- + buffer = malloc(len);
- + if (!buffer) {
- + PERROR("getgrnam_r malloc");
- + ret = -1;
- + goto error;
- + }
- +
- + while ((ret = getgrnam_r(name, &grp, buffer, len, &result)) == ERANGE)
- + {
- + /* Buffer is not big enough, increase its size. */
- + size_t new_len = 2 * len;
- + char *new_buffer = NULL;
- + if (new_len < len) {
- + ERR("getgrnam_r buffer size overflow");
- + ret = -1;
- + goto error;
- + }
- + len = new_len;
- + new_buffer = realloc(buffer, len);
- + if (!new_buffer) {
- + PERROR("getgrnam_r realloc");
- + ret = -1;
- + goto error;
- }
- - return 0;
- + buffer = new_buffer;
- + }
- + if (ret != 0) {
- + PERROR("getgrnam_r");
- + ret = -1;
- + goto error;
- + }
- +
- + /* Group not found. */
- + if (!result) {
- + ret = -1;
- + goto error;
- + }
- +
- + *gid = result->gr_gid;
- + ret = 0;
- +
- +error:
- + free(buffer);
- + if (ret && warn && !warn_once) {
- + WARN("No tracing group detected");
- + warn_once = 1;
- }
- - return grp->gr_gid;
- + return ret;
- }
-
- /*
- diff --git a/src/common/utils.h b/src/common/utils.h
- index 18f19ef1..9c72431d 100644
- --- a/src/common/utils.h
- +++ b/src/common/utils.h
- @@ -22,6 +22,8 @@
- #include <unistd.h>
- #include <stdint.h>
- #include <getopt.h>
- +#include <stdbool.h>
- +#include <sys/types.h>
-
- #define KIBI_LOG2 10
- #define MEBI_LOG2 20
- @@ -52,7 +54,7 @@ int utils_get_count_order_u64(uint64_t x);
- char *utils_get_home_dir(void);
- char *utils_get_user_home_dir(uid_t uid);
- size_t utils_get_current_time_str(const char *format, char *dst, size_t len);
- -gid_t utils_get_group_id(const char *name);
- +int utils_get_group_id(const char *name, bool warn, gid_t *gid);
- char *utils_generate_optstring(const struct option *long_options,
- size_t opt_count);
- int utils_create_lock_file(const char *filepath);
- diff --git a/src/lib/lttng-ctl/lttng-ctl.c b/src/lib/lttng-ctl/lttng-ctl.c
- index 2d84aad9..561b0bcf 100644
- --- a/src/lib/lttng-ctl/lttng-ctl.c
- +++ b/src/lib/lttng-ctl/lttng-ctl.c
- @@ -208,15 +208,13 @@ end:
- LTTNG_HIDDEN
- int lttng_check_tracing_group(void)
- {
- - struct group *grp_tracing; /* no free(). See getgrnam(3) */
- - gid_t *grp_list;
- + gid_t *grp_list, tracing_gid;
- int grp_list_size, grp_id, i;
- int ret = -1;
- const char *grp_name = tracing_group;
-
- /* Get GID of group 'tracing' */
- - grp_tracing = getgrnam(grp_name);
- - if (!grp_tracing) {
- + if (utils_get_group_id(grp_name, false, &tracing_gid)) {
- /* If grp_tracing is NULL, the group does not exist. */
- goto end;
- }
- @@ -241,7 +239,7 @@ int lttng_check_tracing_group(void)
- }
-
- for (i = 0; i < grp_list_size; i++) {
- - if (grp_list[i] == grp_tracing->gr_gid) {
- + if (grp_list[i] == tracing_gid) {
- ret = 1;
- break;
- }
- --
- 2.17.1
-
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