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[libvirt] [PATCHv2 2/3] util: add virGetGroupList



Since neither getpwuid_r() nor initgroups() are safe to call in
between fork and exec (they obtain a mutex, but if some other
thread in the parent also held the mutex at the time of the fork,
the child will deadlock), we have to split out the functionality
that is unsafe.  At least glibc's initgroups() uses getgrouplist
under the hood, so the ideal split is to expose getgrouplist for
use before a fork.  Gnulib already gives us a nice wrapper via
mgetgroups; we wrap it once more to look up by uid instead of name.

* .gnulib: Update for mgetgroups.
* bootstrap.conf (gnulib_modules): Add mgetgroups.
* src/util/virutil.h (virGetGroupList): New declaration.
* src/util/virutil.c (virGetGroupList): New function.
* src/libvirt_private.syms (virutil.h): Export it.

Signed-off-by: Eric Blake <eblake redhat com>
---
 .gnulib                  |  2 +-
 bootstrap.conf           |  1 +
 src/libvirt_private.syms |  1 +
 src/util/virutil.c       | 33 +++++++++++++++++++++++++++++++++
 src/util/virutil.h       |  2 ++
 5 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/.gnulib b/.gnulib
index b72ff2a..da8d59e 160000
--- a/.gnulib
+++ b/.gnulib
@@ -1 +1 @@
-Subproject commit b72ff2a45efde544c406804186d37a3254728571
+Subproject commit da8d59ee79138b85daee1ad5b22ea12e4fb6ce47
diff --git a/bootstrap.conf b/bootstrap.conf
index 410e4f5..1c59c22 100644
--- a/bootstrap.conf
+++ b/bootstrap.conf
@@ -71,6 +71,7 @@ listen
 localeconv
 maintainer-makefile
 manywarnings
+mgetgroups
 mkdtemp
 mkostemp
 mkostemps
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 6df5500..d8b03f1 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -2002,6 +2002,7 @@ virGetDeviceID;
 virGetDeviceUnprivSGIO;
 virGetFCHostNameByWWN;
 virGetGroupID;
+virGetGroupList;
 virGetGroupName;
 virGetHostname;
 virGetUnprivSGIOSysfsPath;
diff --git a/src/util/virutil.c b/src/util/virutil.c
index de7b532..844c694 100644
--- a/src/util/virutil.c
+++ b/src/util/virutil.c
@@ -67,6 +67,7 @@
 #endif

 #include "c-ctype.h"
+#include "mgetgroups.h"
 #include "virerror.h"
 #include "virlog.h"
 #include "virbuffer.h"
@@ -990,6 +991,38 @@ virGetGroupID(const char *group, gid_t *gid)
     return 0;
 }

+
+/* Compute the list of supplementary groups associated with @uid, and
+ * including @gid in the list (unless it is -1), storing a malloc'd
+ * result into @list.  Return the size of the list on success, or -1
+ * on failure with error reported and errno set. May not be called
+ * between fork and exec. */
+int
+virGetGroupList(uid_t uid, gid_t gid, gid_t **list)
+{
+    int ret = -1;
+    char *user = NULL;
+    gid_t group;
+
+    *list = NULL;
+    if (uid == (uid_t)-1)
+        return 0;
+
+    if (!(user = virGetUserEnt(uid, VIR_USER_ENT_NAME, &group)))
+        return -1;
+
+    if (gid == (gid_t)-1)
+        gid = group;
+
+    ret = mgetgroups(user, gid, list);
+    if (ret < 0)
+        virReportSystemError(errno,
+                             _("cannot get group list for '%s'"), user);
+    VIR_FREE(user);
+    return ret;
+}
+
+
 /* Set the real and effective uid and gid to the given values, and call
  * initgroups so that the process has all the assumed group membership of
  * that uid. return 0 on success, -1 on failure (the original system error
diff --git a/src/util/virutil.h b/src/util/virutil.h
index 280a18d..6480b07 100644
--- a/src/util/virutil.h
+++ b/src/util/virutil.h
@@ -115,6 +115,8 @@ char *virGetUserCacheDirectory(void);
 char *virGetUserRuntimeDirectory(void);
 char *virGetUserName(uid_t uid);
 char *virGetGroupName(gid_t gid);
+int virGetGroupList(uid_t uid, gid_t group, gid_t **groups)
+    ATTRIBUTE_NONNULL(3);
 int virGetUserID(const char *name,
                  uid_t *uid) ATTRIBUTE_RETURN_CHECK;
 int virGetGroupID(const char *name,
-- 
1.8.1.4


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