Richard W.M. Jones
2014-Jul-25 13:07 UTC
[Libguestfs] [PATCH] launch: Close file descriptors after fork (RHBZ#1123007).
This refactors existing code to close file descriptors in the recovery
process, and also adds code to close file descriptors between the
fork() and exec() of QEMU or User-Mode Linux.
The reason is to avoid leaking main process file descriptors where the
main process (or other libraries in the main process) are not setting
O_CLOEXEC at all or not setting it atomically. Python is a particular
culprit.
See also this OpenStack Nova bug report:
https://bugs.launchpad.net/nova/+bug/1313477
Thanks: Qin Zhao for identifying and characterizing the problem in Nova.
---
src/guestfs-internal-frontend.h | 16 +++++++++++++++-
src/launch-direct.c | 17 +++++++++--------
src/launch-uml.c | 13 +++++--------
3 files changed, 29 insertions(+), 17 deletions(-)
diff --git a/src/guestfs-internal-frontend.h b/src/guestfs-internal-frontend.h
index 6bf0a94..3129018 100644
--- a/src/guestfs-internal-frontend.h
+++ b/src/guestfs-internal-frontend.h
@@ -1,5 +1,5 @@
/* libguestfs
- * Copyright (C) 2013 Red Hat Inc.
+ * Copyright (C) 2013-2014 Red Hat Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
@@ -161,4 +161,18 @@ extern GUESTFS_DLL_PUBLIC int guestfs___add_libvirt_dom
(guestfs_h *g, virDomain
# define program_name "libguestfs"
#endif
+/* Close all file descriptors matching the condition. */
+#define close_file_descriptors(cond) do { \
+ int max_fd = sysconf (_SC_OPEN_MAX); \
+ int fd; \
+ if (max_fd == -1) \
+ max_fd = 1024; \
+ if (max_fd > 65536) \
+ max_fd = 65536; /* bound the amount of work we do here */ \
+ for (fd = 0; fd < max_fd; ++fd) { \
+ if (cond) \
+ close (fd); \
+ } \
+ } while (0)
+
#endif /* GUESTFS_INTERNAL_FRONTEND_H_ */
diff --git a/src/launch-direct.c b/src/launch-direct.c
index bb73d19..104809d 100644
--- a/src/launch-direct.c
+++ b/src/launch-direct.c
@@ -717,6 +717,13 @@ launch_direct (guestfs_h *g, void *datav, const char *arg)
goto dup_failed;
close (sv[1]);
+
+ /* Close any other file descriptors that we don't want to pass
+ * to qemu. This prevents file descriptors which didn't have
+ * O_CLOEXEC set properly from leaking into the subprocess. See
+ * RHBZ#1123007.
+ */
+ close_file_descriptors (fd >= 2);
}
/* Dump the command line (after setting up stderr above). */
@@ -747,7 +754,7 @@ launch_direct (guestfs_h *g, void *datav, const char *arg)
if (g->recovery_proc) {
r = fork ();
if (r == 0) {
- int i, fd, max_fd;
+ int i;
struct sigaction sa;
pid_t qemu_pid = data->pid;
pid_t parent_pid = getppid ();
@@ -767,13 +774,7 @@ launch_direct (guestfs_h *g, void *datav, const char *arg)
/* Close all other file descriptors. This ensures that we don't
* hold open (eg) pipes from the parent process.
*/
- max_fd = sysconf (_SC_OPEN_MAX);
- if (max_fd == -1)
- max_fd = 1024;
- if (max_fd > 65536)
- max_fd = 65536; /* bound the amount of work we do here */
- for (fd = 0; fd < max_fd; ++fd)
- close (fd);
+ close_file_descriptors (1);
/* It would be nice to be able to put this in the same process
* group as qemu (ie. setpgid (0, qemu_pid)). However this is
diff --git a/src/launch-uml.c b/src/launch-uml.c
index 2a6ddaf..88c684b 100644
--- a/src/launch-uml.c
+++ b/src/launch-uml.c
@@ -333,6 +333,9 @@ launch_uml (guestfs_h *g, void *datav, const char *arg)
goto dup_failed;
close (csv[1]);
+
+ /* RHBZ#1123007 */
+ close_file_descriptors (fd >= 2 && fd != dsv[1]);
}
/* Dump the command line (after setting up stderr above). */
@@ -360,7 +363,7 @@ launch_uml (guestfs_h *g, void *datav, const char *arg)
if (g->recovery_proc) {
r = fork ();
if (r == 0) {
- int i, fd, max_fd;
+ int i;
struct sigaction sa;
pid_t vmlinux_pid = data->pid;
pid_t parent_pid = getppid ();
@@ -380,13 +383,7 @@ launch_uml (guestfs_h *g, void *datav, const char *arg)
/* Close all other file descriptors. This ensures that we don't
* hold open (eg) pipes from the parent process.
*/
- max_fd = sysconf (_SC_OPEN_MAX);
- if (max_fd == -1)
- max_fd = 1024;
- if (max_fd > 65536)
- max_fd = 65536; /* bound the amount of work we do here */
- for (fd = 0; fd < max_fd; ++fd)
- close (fd);
+ close_file_descriptors (1);
/* It would be nice to be able to put this in the same process
* group as vmlinux (ie. setpgid (0, vmlinux_pid)). However
--
1.9.0
Pino Toscano
2014-Jul-25 15:19 UTC
Re: [Libguestfs] [PATCH] launch: Close file descriptors after fork (RHBZ#1123007).
On Friday 25 July 2014 14:07:27 Richard W.M. Jones wrote:> This refactors existing code to close file descriptors in the recovery > process, and also adds code to close file descriptors between the > fork() and exec() of QEMU or User-Mode Linux. > > The reason is to avoid leaking main process file descriptors where the > main process (or other libraries in the main process) are not setting > O_CLOEXEC at all or not setting it atomically. Python is a > particular culprit. > > See also this OpenStack Nova bug report: > https://bugs.launchpad.net/nova/+bug/1313477 > > Thanks: Qin Zhao for identifying and characterizing the problem in > Nova.LGTM. -- Pino Toscano
Qin Zhao
2014-Jul-28 06:35 UTC
Re: [Libguestfs] [PATCH] launch: Close file descriptors after fork (RHBZ#1123007).
Hi Richard,
I see this patch is included into libguestfs >= 1.26.6 & libguestfs
>1.27.24. I feel that version is too high. Now RHEL 7.0 runs
libguestfs-1.22.6, RHEL 6.6 alpha and 6.5 runs libguestfs-1.20.11. Is that
possible to backport this patch, in order to make this problem fixed in
RHEL 7.0, 6.6, and 6.5?
Thanks & Best Regards
Qin Zhao (赵钦)
China System and Technology Lab, IBM
Tel: 86-10-82452339
From: "Richard W.M. Jones" <rjones@redhat.com>
To: libguestfs@redhat.com,
Cc: ptoscano@redhat.com, berrange@redhat.com, Qin
Zhao/China/IBM@IBMCN
Date: 2014/07/25 21:06
Subject: [PATCH] launch: Close file descriptors after fork
(RHBZ#1123007).
This refactors existing code to close file descriptors in the recovery
process, and also adds code to close file descriptors between the
fork() and exec() of QEMU or User-Mode Linux.
The reason is to avoid leaking main process file descriptors where the
main process (or other libraries in the main process) are not setting
O_CLOEXEC at all or not setting it atomically. Python is a particular
culprit.
See also this OpenStack Nova bug report:
https://bugs.launchpad.net/nova/+bug/1313477
Thanks: Qin Zhao for identifying and characterizing the problem in Nova.
---
src/guestfs-internal-frontend.h | 16 +++++++++++++++-
src/launch-direct.c | 17 +++++++++--------
src/launch-uml.c | 13 +++++--------
3 files changed, 29 insertions(+), 17 deletions(-)
diff --git a/src/guestfs-internal-frontend.h
b/src/guestfs-internal-frontend.h
index 6bf0a94..3129018 100644
--- a/src/guestfs-internal-frontend.h
+++ b/src/guestfs-internal-frontend.h
@@ -1,5 +1,5 @@
/* libguestfs
- * Copyright (C) 2013 Red Hat Inc.
+ * Copyright (C) 2013-2014 Red Hat Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
@@ -161,4 +161,18 @@ extern GUESTFS_DLL_PUBLIC int
guestfs___add_libvirt_dom (guestfs_h *g, virDomain
# define program_name "libguestfs"
#endif
+/* Close all file descriptors matching the condition. */
+#define close_file_descriptors(cond) do { \
+ int max_fd = sysconf (_SC_OPEN_MAX); \
+ int fd; \
+ if (max_fd == -1) \
+ max_fd = 1024; \
+ if (max_fd > 65536) \
+ max_fd = 65536; /* bound the amount of work we do here */ \
+ for (fd = 0; fd < max_fd; ++fd) { \
+ if (cond) \
+ close (fd); \
+ } \
+ } while (0)
+
#endif /* GUESTFS_INTERNAL_FRONTEND_H_ */
diff --git a/src/launch-direct.c b/src/launch-direct.c
index bb73d19..104809d 100644
--- a/src/launch-direct.c
+++ b/src/launch-direct.c
@@ -717,6 +717,13 @@ launch_direct (guestfs_h *g, void *datav, const char
*arg)
goto dup_failed;
close (sv[1]);
+
+ /* Close any other file descriptors that we don't want to pass
+ * to qemu. This prevents file descriptors which didn't have
+ * O_CLOEXEC set properly from leaking into the subprocess. See
+ * RHBZ#1123007.
+ */
+ close_file_descriptors (fd >= 2);
}
/* Dump the command line (after setting up stderr above). */
@@ -747,7 +754,7 @@ launch_direct (guestfs_h *g, void *datav, const char
*arg)
if (g->recovery_proc) {
r = fork ();
if (r == 0) {
- int i, fd, max_fd;
+ int i;
struct sigaction sa;
pid_t qemu_pid = data->pid;
pid_t parent_pid = getppid ();
@@ -767,13 +774,7 @@ launch_direct (guestfs_h *g, void *datav, const char
*arg)
/* Close all other file descriptors. This ensures that we don't
* hold open (eg) pipes from the parent process.
*/
- max_fd = sysconf (_SC_OPEN_MAX);
- if (max_fd == -1)
- max_fd = 1024;
- if (max_fd > 65536)
- max_fd = 65536; /* bound the amount of work we do here */
- for (fd = 0; fd < max_fd; ++fd)
- close (fd);
+ close_file_descriptors (1);
/* It would be nice to be able to put this in the same process
* group as qemu (ie. setpgid (0, qemu_pid)). However this is
diff --git a/src/launch-uml.c b/src/launch-uml.c
index 2a6ddaf..88c684b 100644
--- a/src/launch-uml.c
+++ b/src/launch-uml.c
@@ -333,6 +333,9 @@ launch_uml (guestfs_h *g, void *datav, const char *arg)
goto dup_failed;
close (csv[1]);
+
+ /* RHBZ#1123007 */
+ close_file_descriptors (fd >= 2 && fd != dsv[1]);
}
/* Dump the command line (after setting up stderr above). */
@@ -360,7 +363,7 @@ launch_uml (guestfs_h *g, void *datav, const char *arg)
if (g->recovery_proc) {
r = fork ();
if (r == 0) {
- int i, fd, max_fd;
+ int i;
struct sigaction sa;
pid_t vmlinux_pid = data->pid;
pid_t parent_pid = getppid ();
@@ -380,13 +383,7 @@ launch_uml (guestfs_h *g, void *datav, const char
*arg)
/* Close all other file descriptors. This ensures that we don't
* hold open (eg) pipes from the parent process.
*/
- max_fd = sysconf (_SC_OPEN_MAX);
- if (max_fd == -1)
- max_fd = 1024;
- if (max_fd > 65536)
- max_fd = 65536; /* bound the amount of work we do here */
- for (fd = 0; fd < max_fd; ++fd)
- close (fd);
+ close_file_descriptors (1);
/* It would be nice to be able to put this in the same process
* group as vmlinux (ie. setpgid (0, vmlinux_pid)). However
--
1.9.0
Richard W.M. Jones
2014-Jul-28 08:42 UTC
Re: [Libguestfs] [PATCH] launch: Close file descriptors after fork (RHBZ#1123007).
On Mon, Jul 28, 2014 at 02:35:22PM +0800, Qin Zhao wrote:> Hi Richard, > > I see this patch is included into libguestfs >= 1.26.6 & libguestfs >> 1.27.24. I feel that version is too high. Now RHEL 7.0 runs > libguestfs-1.22.6, RHEL 6.6 alpha and 6.5 runs libguestfs-1.20.11. Is that > possible to backport this patch, in order to make this problem fixed in > RHEL 7.0, 6.6, and 6.5?Please open two bugs for it against RHEL 6 & RHEL 7 using the links below: https://bugzilla.redhat.com/enter_bug.cgi?product=Red%20Hat%20Enterprise%20Linux%206&component=libguestfs https://bugzilla.redhat.com/enter_bug.cgi?product=Red%20Hat%20Enterprise%20Linux%207&component=libguestfs Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-builder quickly builds VMs from scratch http://libguestfs.org/virt-builder.1.html
Seemingly Similar Threads
- Re: [PATCH] launch: Close file descriptors after fork (RHBZ#1123007).
- [PATCH v2] launch: Close file descriptors after fork (RHBZ#1123007).
- [PATCH] lib: direct, uml: Unblock SIGTERM in the hypervisor and recovery processes (RHBZ#1460338).
- [PATCH v2 0/4] Experimental User-Mode Linux backend.
- [PATCH 0/4] Not quite working User-Mode Linux backend.