shared: procfs_file_alloca: handle pid==0

when pid is set to 0 use /proc/self

4 files changed, 17 insertions, 43 deletions

diff --git a/src/shared/audit.c b/src/shared/audit.c
index 9ab46408da..8038ac3c12 100644
--- a/src/shared/audit.c
+++ b/src/shared/audit.c
@@ -46,10 +46,7 @@ int audit_session_from_pid(pid_t pid, uint32_t *id) {
         if (detect_container(NULL) > 0)
                 return -ENOTSUP;
 
-        if (pid == 0)
-                p = "/proc/self/sessionid";
-        else
-                p = procfs_file_alloca(pid, "sessionid");
+        p = procfs_file_alloca(pid, "sessionid");
 
         r = read_one_line_file(p, &s);
         if (r < 0)
@@ -78,10 +75,7 @@ int audit_loginuid_from_pid(pid_t pid, uid_t *uid) {
         if (detect_container(NULL) > 0)
                 return -ENOTSUP;
 
-        if (pid == 0)
-                p = "/proc/self/loginuid";
-        else
-                p = procfs_file_alloca(pid, "loginuid");
+        p = procfs_file_alloca(pid, "loginuid");
 
         r = read_one_line_file(p, &s);
         if (r < 0)
diff --git a/src/shared/cgroup-util.c b/src/shared/cgroup-util.c
index f2af8dcfda..855c9cd160 100644
--- a/src/shared/cgroup-util.c
+++ b/src/shared/cgroup-util.c
@@ -746,10 +746,7 @@ int cg_pid_get_path(const char *controller, pid_t pid, char **path) {
         } else
                 controller = SYSTEMD_CGROUP_CONTROLLER;
 
-        if (pid == 0)
-                fs = "/proc/self/cgroup";
-        else
-                fs = procfs_file_alloca(pid, "cgroup");
+        fs = procfs_file_alloca(pid, "cgroup");
 
         f = fopen(fs, "re");
         if (!f)
diff --git a/src/shared/util.c b/src/shared/util.c
index f491708f4f..50dac70804 100644
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -495,10 +495,7 @@ int get_starttime_of_pid(pid_t pid, unsigned long long *st) {
         assert(pid >= 0);
         assert(st);
 
-        if (pid == 0)
-                p = "/proc/self/stat";
-        else
-                p = procfs_file_alloca(pid, "stat");
+        p = procfs_file_alloca(pid, "stat");
 
         f = fopen(p, "re");
         if (!f)
@@ -573,10 +570,7 @@ int get_process_comm(pid_t pid, char **name) {
         assert(name);
         assert(pid >= 0);
 
-        if (pid == 0)
-                p = "/proc/self/comm";
-        else
-                p = procfs_file_alloca(pid, "comm");
+        p = procfs_file_alloca(pid, "comm");
 
         r = read_one_line_file(p, name);
         if (r == -ENOENT)
@@ -594,10 +588,7 @@ int get_process_cmdline(pid_t pid, size_t max_length, bool comm_fallback, char *
         assert(line);
         assert(pid >= 0);
 
-        if (pid == 0)
-                p = "/proc/self/cmdline";
-        else
-                p = procfs_file_alloca(pid, "cmdline");
+        p = procfs_file_alloca(pid, "cmdline");
 
         f = fopen(p, "re");
         if (!f)
@@ -716,10 +707,7 @@ int get_process_capeff(pid_t pid, char **capeff) {
         assert(capeff);
         assert(pid >= 0);
 
-        if (pid == 0)
-                p = "/proc/self/status";
-        else
-                p = procfs_file_alloca(pid, "status");
+        p = procfs_file_alloca(pid, "status");
 
         return get_status_field(p, "\nCapEff:", capeff);
 }
@@ -732,10 +720,7 @@ int get_process_exe(pid_t pid, char **name) {
         assert(pid >= 0);
         assert(name);
 
-        if (pid == 0)
-                p = "/proc/self/exe";
-        else
-                p = procfs_file_alloca(pid, "exe");
+        p = procfs_file_alloca(pid, "exe");
 
         r = readlink_malloc(p, name);
         if (r < 0)
@@ -2549,10 +2534,7 @@ int get_ctty_devnr(pid_t pid, dev_t *d) {
 
         assert(pid >= 0);
 
-        if (pid == 0)
-                fn = "/proc/self/stat";
-        else
-                fn = procfs_file_alloca(pid, "stat");
+        fn = procfs_file_alloca(pid, "stat");
 
         f = fopen(fn, "re");
         if (!f)
@@ -5095,10 +5077,7 @@ int getenv_for_pid(pid_t pid, const char *field, char **_value) {
         assert(field);
         assert(_value);
 
-        if (pid == 0)
-                path = "/proc/self/environ";
-        else
-                path = procfs_file_alloca(pid, "environ");
+        path = procfs_file_alloca(pid, "environ");
 
         f = fopen(path, "re");
         if (!f)
diff --git a/src/shared/util.h b/src/shared/util.h
index d9720d0a36..8645654267 100644
--- a/src/shared/util.h
+++ b/src/shared/util.h
@@ -777,9 +777,13 @@ int unlink_noerrno(const char *path);
 #define procfs_file_alloca(pid, field)                                  \
         ({                                                              \
                 pid_t _pid_ = (pid);                                    \
-                char *_r_;                                              \
-                _r_ = alloca(sizeof("/proc/") -1 + DECIMAL_STR_MAX(pid_t) + 1 + sizeof(field)); \
-                sprintf(_r_, "/proc/"PID_FMT"/" field, _pid_); \
+                const char *_r_;                                        \
+                if (_pid_ == 0) {                                       \
+                        _r_ = ("/proc/self/" field);                    \
+                } else {                                                \
+                        _r_ = alloca(strlen("/proc/") + DECIMAL_STR_MAX(pid_t) + 1 + sizeof(field)); \
+                        sprintf((char*) _r_, "/proc/"PID_FMT"/" field, _pid_);                       \
+                }                                                       \
                 _r_;                                                    \
         })