util: define union dirent_storage and make use of it everywhere

Make sure to allocate enough space for readdir_r().

https://bugzilla.redhat.com/show_bug.cgi?id=858754

5 files changed, 31 insertions, 16 deletions

diff --git a/src/shared/conf-files.c b/src/shared/conf-files.c
index 83e4cce156..34b86293d3 100644
--- a/src/shared/conf-files.c
+++ b/src/shared/conf-files.c
@@ -39,7 +39,6 @@
 
 static int files_add(Hashmap *h, const char *path, const char *suffix) {
         DIR *dir;
-        struct dirent buffer, *de;
         int r = 0;
 
         dir = opendir(path);
@@ -50,10 +49,12 @@ static int files_add(Hashmap *h, const char *path, const char *suffix) {
         }
 
         for (;;) {
+                struct dirent *de;
+                union dirent_storage buf;
                 int k;
                 char *p;
 
-                k = readdir_r(dir, &buffer, &de);
+                k = readdir_r(dir, &buf.de, &de);
                 if (k != 0) {
                         r = -k;
                         goto finish;
diff --git a/src/shared/hwclock.c b/src/shared/hwclock.c
index 67eb2eff8b..b93855d957 100644
--- a/src/shared/hwclock.c
+++ b/src/shared/hwclock.c
@@ -61,10 +61,11 @@ static int rtc_open(int flags) {
 
         for (;;) {
                 char *p, *v;
-                struct dirent buf, *de;
+                struct dirent *de;
+                union dirent_storage buf;
                 int r;
 
-                r = readdir_r(d, &buf, &de);
+                r = readdir_r(d, &buf.de, &de);
                 if (r != 0)
                         goto fallback;
 
diff --git a/src/shared/install.c b/src/shared/install.c
index f30bf8317b..a99c757ea8 100644
--- a/src/shared/install.c
+++ b/src/shared/install.c
@@ -201,7 +201,6 @@ static int remove_marked_symlinks_fd(
 
         int r = 0;
         DIR *d;
-        struct dirent buffer, *de;
 
         assert(remove_symlinks_to);
         assert(fd >= 0);
@@ -218,9 +217,11 @@ static int remove_marked_symlinks_fd(
         rewinddir(d);
 
         for (;;) {
+                struct dirent *de;
+                union dirent_storage buf;
                 int k;
 
-                k = readdir_r(d, &buffer, &de);
+                k = readdir_r(d, &buf.de, &de);
                 if (k != 0) {
                         r = -errno;
                         break;
@@ -375,7 +376,6 @@ static int find_symlinks_fd(
 
         int r = 0;
         DIR *d;
-        struct dirent buffer, *de;
 
         assert(name);
         assert(fd >= 0);
@@ -391,8 +391,10 @@ static int find_symlinks_fd(
 
         for (;;) {
                 int k;
+                struct dirent *de;
+                union dirent_storage buf;
 
-                k = readdir_r(d, &buffer, &de);
+                k = readdir_r(d, &buf.de, &de);
                 if (k != 0) {
                         r = -errno;
                         break;
@@ -1906,7 +1908,6 @@ int unit_file_get_list(
                 return r;
 
         STRV_FOREACH(i, paths.unit_path) {
-                struct dirent buffer, *de;
                 const char *units_dir;
 
                 free(buf);
@@ -1934,9 +1935,11 @@ int unit_file_get_list(
                 }
 
                 for (;;) {
+                        struct dirent *de;
+                        union dirent_storage buffer;
                         UnitFileList *f;
 
-                        r = readdir_r(d, &buffer, &de);
+                        r = readdir_r(d, &buffer.de, &de);
                         if (r != 0) {
                                 r = -r;
                                 goto finish;
diff --git a/src/shared/util.c b/src/shared/util.c
index 69c9437db8..b48bad4c46 100644
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -2956,9 +2956,10 @@ int dir_is_empty(const char *path) {
                 return -errno;
 
         for (;;) {
-                struct dirent buf, *de;
+                struct dirent *de;
+                union dirent_storage buf;
 
-                r = readdir_r(d, &buf, &de);
+                r = readdir_r(d, &buf.de, &de);
                 if (r > 0)
                         return -r;
 
@@ -3260,12 +3261,13 @@ int rm_rf_children_dangerous(int fd, bool only_dirs, bool honour_sticky, struct
         }
 
         for (;;) {
-                struct dirent buf, *de;
+                struct dirent *de;
+                union dirent_storage buf;
                 bool is_dir, keep_around;
                 struct stat st;
                 int r;
 
-                r = readdir_r(d, &buf, &de);
+                r = readdir_r(d, &buf.de, &de);
                 if (r != 0 && ret == 0) {
                         ret = -r;
                         break;
@@ -4942,10 +4944,11 @@ int get_files_in_directory(const char *path, char ***list) {
                 return -errno;
 
         for (;;) {
-                struct dirent buffer, *de;
+                struct dirent *de;
+                union dirent_storage buf;
                 int k;
 
-                k = readdir_r(d, &buffer, &de);
+                k = readdir_r(d, &buf.de, &de);
                 if (k != 0) {
                         r = -k;
                         goto finish;
diff --git a/src/shared/util.h b/src/shared/util.h
index 2429339f5b..e5728bd87e 100644
--- a/src/shared/util.h
+++ b/src/shared/util.h
@@ -35,6 +35,7 @@
 #include <sys/stat.h>
 #include <dirent.h>
 #include <sys/resource.h>
+#include <stddef.h>
 
 #include "macro.h"
 
@@ -46,6 +47,12 @@ typedef struct dual_timestamp {
         usec_t monotonic;
 } dual_timestamp;
 
+union dirent_storage {
+        struct dirent de;
+        uint8_t storage[offsetof(struct dirent, d_name) +
+                        ((NAME_MAX + 1 + sizeof(long)) & ~(sizeof(long) - 1))];
+};
+
 #define MSEC_PER_SEC  1000ULL
 #define USEC_PER_SEC  1000000ULL
 #define USEC_PER_MSEC 1000ULL