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[libvirt] [PATCH 6/8] util: new virCommandSetMax(MemLock|Processes|Files)



This patch adds two sets of functions:

1) lower level functions that will immediately set the
RLIMIT_MEMLOCK. RLIMIT_NPROC, or RLIMIT_NOFILE of either the current
process (using setrlimit()) or any other process (using prlimit()).

2) functions for virCommand* that will setup a virCommand object to
set those limits at a later time just after it has forked a new
process, but before it execs the new program.

configure.ac has prlimit and setrlimit added to the list of functions
to check for, and the low level functions are hopefully properly
"unsupported" error) on all platforms.

You'll notice some ugly typecasting around pid_t; this is all an
attempt to follow the formula given to me by Eric for getting it to
compile without warnings on all platforms.
---
 configure.ac             |   2 +-
 src/libvirt_private.syms |   6 ++
 src/util/vircommand.c    |  38 ++++++++++++
 src/util/vircommand.h    |   4 ++
 src/util/virutil.c       | 146 +++++++++++++++++++++++++++++++++++++++++++++++
 src/util/virutil.h       |   4 ++
 6 files changed, 199 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index 89dae3d..23c24d2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -194,7 +194,7 @@ dnl Availability of various common functions (non-fatal if missing),
 dnl and various less common threadsafe functions
 AC_CHECK_FUNCS_ONCE([cfmakeraw geteuid getgid getgrnam_r getmntent_r \
   getpwuid_r getuid initgroups kill mmap newlocale posix_fallocate \
-  posix_memalign regexec sched_getaffinity setns symlink])
+  posix_memalign prlimit regexec sched_getaffinity setns setrlimit symlink])
 
 dnl Availability of pthread functions (if missing, win32 threading is
 dnl assumed).  Because of $LIB_PTHREAD, we cannot use AC_CHECK_FUNCS_ONCE.
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 2a2c40e..c988c21 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -1185,6 +1185,9 @@ virCommandSetErrorFD;
 virCommandSetGID;
 virCommandSetInputBuffer;
 virCommandSetInputFD;
+virCommandSetMaxFiles;
+virCommandSetMaxMemLock;
+virCommandSetMaxProcesses;
 virCommandSetOutputBuffer;
 virCommandSetOutputFD;
 virCommandSetPidFile;
@@ -1904,6 +1907,9 @@ virSetBlocking;
 virSetCloseExec;
 virSetDeviceUnprivSGIO;
 virSetInherit;
+virSetMaxFiles;
+virSetMaxMemLock;
+virSetMaxProcesses;
 virSetNonBlock;
 virSetUIDGID;
 virSetUIDGIDWithCaps;
diff --git a/src/util/vircommand.c b/src/util/vircommand.c
index ac56a63..d0def8c 100644
--- a/src/util/vircommand.c
+++ b/src/util/vircommand.c
@@ -107,6 +107,10 @@ struct _virCommand {
     char *pidfile;
     bool reap;
 
+    unsigned long long maxMemLock;
+    unsigned int maxProcesses;
+    unsigned int maxFiles;
+
     uid_t uid;
     gid_t gid;
     unsigned long long capabilities;
@@ -598,6 +602,13 @@ virExec(virCommandPtr cmd)
         goto fork_error;
     }
 
+    if (virSetMaxMemLock(-1, cmd->maxMemLock) < 0)
+        goto fork_error;
+    if (virSetMaxProcesses(-1, cmd->maxProcesses) < 0)
+        goto fork_error;
+    if (virSetMaxFiles(-1, cmd->maxFiles) < 0)
+        goto fork_error;
+
     if (cmd->hook) {
         VIR_DEBUG("Run hook %p %p", cmd->hook, cmd->opaque);
         ret = cmd->hook(cmd->opaque);
@@ -958,6 +969,33 @@ virCommandSetUID(virCommandPtr cmd, uid_t uid)
     cmd->uid = uid;
 }
 
+void
+virCommandSetMaxMemLock(virCommandPtr cmd, unsigned long long bytes)
+{
+    if (!cmd || cmd->has_error)
+        return;
+
+    cmd->maxMemLock = bytes;
+}
+
+void
+virCommandSetMaxProcesses(virCommandPtr cmd, unsigned int procs)
+{
+    if (!cmd || cmd->has_error)
+        return;
+
+    cmd->maxProcesses = procs;
+}
+
+void
+virCommandSetMaxFiles(virCommandPtr cmd, unsigned int files)
+{
+    if (!cmd || cmd->has_error)
+        return;
+
+    cmd->maxFiles = files;
+}
+
 /**
  * virCommandClearCaps:
  * @cmd: the command to modify
diff --git a/src/util/vircommand.h b/src/util/vircommand.h
index 6c13795..18568fe 100644
--- a/src/util/vircommand.h
+++ b/src/util/vircommand.h
@@ -65,6 +65,10 @@ void virCommandSetGID(virCommandPtr cmd, gid_t gid);
 
 void virCommandSetUID(virCommandPtr cmd, uid_t uid);
 
+void virCommandSetMaxMemLock(virCommandPtr cmd, unsigned long long bytes);
+void virCommandSetMaxProcesses(virCommandPtr cmd, unsigned int procs);
+void virCommandSetMaxFiles(virCommandPtr cmd, unsigned int files);
+
 void virCommandClearCaps(virCommandPtr cmd);
 
 void virCommandAllowCap(virCommandPtr cmd,
diff --git a/src/util/virutil.c b/src/util/virutil.c
index b9de33c..058a069 100644
--- a/src/util/virutil.c
+++ b/src/util/virutil.c
@@ -38,6 +38,10 @@
 #include <sys/types.h>
 #include <sys/ioctl.h>
 #include <sys/wait.h>
+#if HAVE_SETRLIMIT
+# include <sys/time.h>
+# include <sys/resource.h>
+#endif
 #if HAVE_MMAP
 # include <sys/mman.h>
 #endif
@@ -2992,6 +2996,148 @@ virGetGroupName(gid_t gid ATTRIBUTE_UNUSED)
 }
 #endif /* HAVE_GETPWUID_R */
 
+#if HAVE_SETRLIMIT
+
+# if HAVE_PRLIMIT
+static int
+virPrLimit(pid_t pid, int resource, struct rlimit *rlim)
+{
+    return prlimit(pid, resource, rlim, NULL);
+}
+# else
+static int
+virPrLimit(pid_t pid ATTRIBUTE_UNUSED,
+           int resource ATTRIBUTE_UNUSED,
+           struct rlimit *rlim ATTRIBUTE_UNUSED)
+{
+    virReportSystemError(ENOSYS, "%s", _("Not supported on this platform"));
+    return -1;
+}
+# endif
+
+int
+virSetMaxMemLock(pid_t pid, unsigned long long bytes)
+{
+    struct rlimit rlim;
+
+    if (bytes == 0)
+        return 0;
+
+    rlim.rlim_cur = rlim.rlim_max = bytes;
+    if (pid == (pid_t)-1) {
+        if (setrlimit(RLIMIT_MEMLOCK, &rlim) < 0) {
+            virReportSystemError(errno,
+                                 _("cannot limit locked memory to %llu"),
+                                 bytes);
+            return -1;
+        }
+    } else {
+        if (virPrLimit(pid, RLIMIT_MEMLOCK, &rlim) < 0) {
+            virReportSystemError(errno,
+                                 _("cannot limit locked memory "
+                                   "of process %lld to %llu"),
+                                 (long long int)pid, bytes);
+            return -1;
+        }
+    }
+    return 0;
+}
+
+int
+virSetMaxProcesses(pid_t pid, unsigned int procs)
+{
+    struct rlimit rlim;
+
+    if (procs == 0)
+        return 0;
+
+    rlim.rlim_cur = rlim.rlim_max = procs;
+    if (pid == (pid_t)-1) {
+        if (setrlimit(RLIMIT_NPROC, &rlim) < 0) {
+            virReportSystemError(errno,
+                                 _("cannot limit number of subprocesses to %u"),
+                                 procs);
+            return -1;
+        }
+    } else {
+        if (virPrLimit(pid, RLIMIT_NPROC, &rlim) < 0) {
+            virReportSystemError(errno,
+                                 _("cannot limit number of subprocesses "
+                                   "of process %lld to %u"),
+                                 (long long int)pid, procs);
+            return -1;
+        }
+    }
+    return 0;
+}
+
+int
+virSetMaxFiles(pid_t pid, unsigned int files)
+{
+    struct rlimit rlim;
+
+    if (files == 0)
+        return 0;
+
+   /* Max number of opened files is one greater than actual limit. See
+    * man setrlimit.
+    *
+    * NB: That indicates to me that we would want the following code
+    * to say "files - 1", but the original of this code in
+    * qemu_process.c also had files + 1, so this preserves current
+    * behavior.
+    */
+    rlim.rlim_cur = rlim.rlim_max = files + 1;
+    if (pid == (pid_t)-1) {
+        if (setrlimit(RLIMIT_NOFILE, &rlim) < 0) {
+            virReportSystemError(errno,
+                                 _("cannot limit number of open files to %u"),
+                                 files);
+            return -1;
+        }
+    } else {
+        if (virPrLimit(pid, RLIMIT_NOFILE, &rlim) < 0) {
+            virReportSystemError(errno,
+                                 _("cannot limit number of open files "
+                                   "of process %lld to %u"),
+                                 (long long int)pid, files);
+            return -1;
+        }
+    }
+    return 0;
+}
+#else
+int
+virSetMaxMemLock(pid_t pid ATTRIBUTE_UNUSED, unsigned long long bytes)
+{
+    if (bytes == 0)
+        return 0;
+
+    virReportSystemError(ENOSYS, "%s", _("Not supported on this platform"));
+    return -1;
+}
+
+int
+virSetMaxProcesses(pid_t pid ATTRIBUTE_UNUSED, unsigned int procs)
+{
+    if (procs == 0)
+        return 0;
+
+    virReportSystemError(ENOSYS, "%s", _("Not supported on this platform"));
+    return -1;
+}
+
+int
+virSetMaxFiles(pid_t pid ATTRIBUTE_UNUSED, unsigned int files)
+{
+    if (files == 0)
+        return 0;
+
+    virReportSystemError(ENOSYS, "%s", _("Not supported on this platform"));
+    return -1;
+}
+#endif
+
 #if WITH_CAPNG
 /* Set the real and effective uid and gid to the given values, while
  * maintaining the capabilities indicated by bits in @capBits. Return
diff --git a/src/util/virutil.h b/src/util/virutil.h
index 39033db..8b258c9 100644
--- a/src/util/virutil.h
+++ b/src/util/virutil.h
@@ -53,6 +53,10 @@ int virSetCloseExec(int fd) ATTRIBUTE_RETURN_CHECK;
 int virPipeReadUntilEOF(int outfd, int errfd,
                         char **outbuf, char **errbuf);
 
+int virSetMaxMemLock(pid_t pid, unsigned long long bytes);
+int virSetMaxProcesses(pid_t pid, unsigned int procs);
+int virSetMaxFiles(pid_t pid, unsigned int files);
+
 int virSetUIDGID(uid_t uid, gid_t gid);
 int virSetUIDGIDWithCaps(uid_t uid, gid_t gid, unsigned long long capBits,
                          bool clearExistingCaps);
-- 
1.7.11.7


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