From 370c860f748d149097710dc7952a64f627db9de7 Mon Sep 17 00:00:00 2001
From: Dave Reisner <dreisner@archlinux.org>
Date: Sat, 19 Apr 2014 13:22:35 -0400
Subject: [PATCH] implement a union to pad out file_handle

Cases where name_to_handle_at is used allocated the full struct to be
MAX_HANDLE_SZ, and assigned this size to handle_bytes. This is wrong
since handle_bytes should describe the length of the flexible array
member and not the whole struct.

Define a union type which includes sufficient padding to allow
assignment of MAX_HANDLE_SZ to be correct.
---
 src/libudev/libudev-monitor.c    |    6 ++----
 src/readahead/readahead-common.c |    6 ++----
 src/shared/util.h                |    6 ++++++
 src/tmpfiles/tmpfiles.c          |   11 ++++-------
 4 files changed, 14 insertions(+), 15 deletions(-)

diff --git src/libudev/libudev-monitor.c src/libudev/libudev-monitor.c
index 3f7436b..0a2ab82 100644
--- src/libudev/libudev-monitor.c
+++ src/libudev/libudev-monitor.c
@@ -108,15 +108,13 @@ static struct udev_monitor *udev_monitor_new(struct udev *udev)
 
 /* we consider udev running when /dev is on devtmpfs */
 static bool udev_has_devtmpfs(struct udev *udev) {
-        struct file_handle *h;
+        union file_handle_union h = { .handle.handle_bytes = MAX_HANDLE_SZ, };
         int mount_id;
         _cleanup_fclose_ FILE *f = NULL;
         char line[LINE_MAX], *e;
         int r;
 
-        h = alloca(MAX_HANDLE_SZ);
-        h->handle_bytes = MAX_HANDLE_SZ;
-        r = name_to_handle_at(AT_FDCWD, "/dev", h, &mount_id, 0);
+        r = name_to_handle_at(AT_FDCWD, "/dev", &h.handle, &mount_id, 0);
         if (r < 0)
                 return false;
 
diff --git src/readahead/readahead-common.c src/readahead/readahead-common.c
index 5ffa88b..49679fc 100644
--- src/readahead/readahead-common.c
+++ src/readahead/readahead-common.c
@@ -75,7 +75,7 @@ int fs_on_ssd(const char *p) {
         if (major(st.st_dev) == 0) {
                 _cleanup_fclose_ FILE *f = NULL;
                 int mount_id;
-                struct file_handle *h;
+                union file_handle_union h = { .handle.handle_bytes = MAX_HANDLE_SZ, };
 
                 /* Might be btrfs, which exposes "ssd" as mount flag if it is on ssd.
                  *
@@ -83,9 +83,7 @@ int fs_on_ssd(const char *p) {
                  * and then lookup the mount ID in mountinfo to find
                  * the mount options. */
 
-                h = alloca(MAX_HANDLE_SZ);
-                h->handle_bytes = MAX_HANDLE_SZ;
-                r = name_to_handle_at(AT_FDCWD, p, h, &mount_id, AT_SYMLINK_FOLLOW);
+                r = name_to_handle_at(AT_FDCWD, p, &h.handle, &mount_id, AT_SYMLINK_FOLLOW);
                 if (r < 0)
                         return false;
 
diff --git src/shared/util.h src/shared/util.h
index 900f1cf..891848a 100644
--- src/shared/util.h
+++ src/shared/util.h
@@ -22,6 +22,7 @@
 ***/
 
 #include <alloca.h>
+#include <fcntl.h>
 #include <inttypes.h>
 #include <time.h>
 #include <sys/time.h>
@@ -883,3 +884,8 @@ int fd_warn_permissions(const char *path
 
 unsigned long personality_from_string(const char *p);
 const char *personality_to_string(unsigned long);
+
+union file_handle_union {
+  struct file_handle handle;
+  char padding[sizeof(struct file_handle) + MAX_HANDLE_SZ];
+};
diff --git src/tmpfiles/tmpfiles.c src/tmpfiles/tmpfiles.c
index 33e7cbc..04b472d 100644
--- src/tmpfiles/tmpfiles.c
+++ src/tmpfiles/tmpfiles.c
@@ -217,19 +217,16 @@ static bool unix_socket_alive(const char *fn) {
 }
 
 static int dir_is_mount_point(DIR *d, const char *subdir) {
-        struct file_handle *h;
+        union file_handle_union h = { .handle.handle_bytes = MAX_HANDLE_SZ };
         int mount_id_parent, mount_id;
         int r_p, r;
 
-        h = alloca(MAX_HANDLE_SZ);
-
-        h->handle_bytes = MAX_HANDLE_SZ;
-        r_p = name_to_handle_at(dirfd(d), ".", h, &mount_id_parent, 0);
+        r_p = name_to_handle_at(dirfd(d), ".", &h.handle, &mount_id_parent, 0);
         if (r_p < 0)
                 r_p = -errno;
 
-        h->handle_bytes = MAX_HANDLE_SZ;
-        r = name_to_handle_at(dirfd(d), subdir, h, &mount_id, 0);
+        h.handle.handle_bytes = MAX_HANDLE_SZ;
+        r = name_to_handle_at(dirfd(d), subdir, &h.handle, &mount_id, 0);
         if (r < 0)
                 r = -errno;
 
-- 
1.7.9.2

