[kernel] r21777 - in dists/trunk/linux/debian: . patches patches/bugfix/all
Ben Hutchings
benh at moszumanska.debian.org
Sun Sep 7 22:57:21 UTC 2014
Author: benh
Date: Sun Sep 7 22:57:20 2014
New Revision: 21777
Log:
mnt: Fix flag handling on remount (CVE-2014-5206)
- mnt: Only change user settable mount flags in remount
- mnt: Move the test for MNT_LOCK_READONLY from change_mount_flags into
do_remount
- mnt: Correct permission checks in do_remount
- mnt: Change the default remount atime from relatime to the existing value
- mnt: Add tests for unprivileged remount cases that have found to be faulty
Added:
dists/trunk/linux/debian/patches/bugfix/all/mnt-Add-tests-for-unprivileged-remount-cases-that-ha.patch
dists/trunk/linux/debian/patches/bugfix/all/mnt-Change-the-default-remount-atime-from-relatime-t.patch
dists/trunk/linux/debian/patches/bugfix/all/mnt-Correct-permission-checks-in-do_remount.patch
dists/trunk/linux/debian/patches/bugfix/all/mnt-Move-the-test-for-MNT_LOCK_READONLY-from-change_.patch
dists/trunk/linux/debian/patches/bugfix/all/mnt-Only-change-user-settable-mount-flags-in-remount.patch
Modified:
dists/trunk/linux/debian/changelog
dists/trunk/linux/debian/patches/series
Modified: dists/trunk/linux/debian/changelog
==============================================================================
--- dists/trunk/linux/debian/changelog Sun Sep 7 20:46:18 2014 (r21776)
+++ dists/trunk/linux/debian/changelog Sun Sep 7 22:57:20 2014 (r21777)
@@ -3,6 +3,8 @@
* New upstream stable update (closes: #748615):
https://www.kernel.org/pub/linux/kernel/v3.x/ChangeLog-3.16.1
https://www.kernel.org/pub/linux/kernel/v3.x/ChangeLog-3.16.2
+ - kvm: iommu: fix the third parameter of kvm_iommu_put_pages
+ (CVE-2014-3601)
[ Ben Hutchings ]
* HID: Enable HID_RMI as module (Closes: #754519)
@@ -31,6 +33,14 @@
* sound: Disable SND_CS5535AUDIO on all but i386 and mips*/loongson-2f
* [mips*/loongson-2f] video: Re-add and enable sm7xxfb driver, removed
upstream in 3.15
+ * mnt: Fix flag handling on remount (CVE-2014-5206)
+ - mnt: Only change user settable mount flags in remount
+ - mnt: Move the test for MNT_LOCK_READONLY from change_mount_flags into
+ do_remount
+ - mnt: Correct permission checks in do_remount
+ - mnt: Change the default remount atime from relatime to the existing value
+ - mnt: Add tests for unprivileged remount cases that have found to be
+ faulty
[ Vagrant Cascadian ]
* [armmp] Enable IMX_IPUV3_CORE (closes: #756810).
Added: dists/trunk/linux/debian/patches/bugfix/all/mnt-Add-tests-for-unprivileged-remount-cases-that-ha.patch
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ dists/trunk/linux/debian/patches/bugfix/all/mnt-Add-tests-for-unprivileged-remount-cases-that-ha.patch Sun Sep 7 22:57:20 2014 (r21777)
@@ -0,0 +1,315 @@
+From: "Eric W. Biederman" <ebiederm at xmission.com>
+Date: Tue, 29 Jul 2014 15:50:44 -0700
+Subject: [5/5] mnt: Add tests for unprivileged remount cases that have found
+ to be faulty
+Origin: https://git.kernel.org/linus/db181ce011e3c033328608299cd6fac06ea50130
+
+Kenton Varda <kenton at sandstorm.io> discovered that by remounting a
+read-only bind mount read-only in a user namespace the
+MNT_LOCK_READONLY bit would be cleared, allowing an unprivileged user
+to the remount a read-only mount read-write.
+
+Upon review of the code in remount it was discovered that the code allowed
+nosuid, noexec, and nodev to be cleared. It was also discovered that
+the code was allowing the per mount atime flags to be changed.
+
+The first naive patch to fix these issues contained the flaw that using
+default atime settings when remounting a filesystem could be disallowed.
+
+To avoid this problems in the future add tests to ensure unprivileged
+remounts are succeeding and failing at the appropriate times.
+
+Cc: stable at vger.kernel.org
+Acked-by: Serge E. Hallyn <serge.hallyn at ubuntu.com>
+Signed-off-by: "Eric W. Biederman" <ebiederm at xmission.com>
+---
+ tools/testing/selftests/Makefile | 1 +
+ tools/testing/selftests/mount/Makefile | 17 ++
+ .../selftests/mount/unprivileged-remount-test.c | 242 +++++++++++++++++++++
+ 3 files changed, 260 insertions(+)
+ create mode 100644 tools/testing/selftests/mount/Makefile
+ create mode 100644 tools/testing/selftests/mount/unprivileged-remount-test.c
+
+diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
+index e66e710..0a8a9db 100644
+--- a/tools/testing/selftests/Makefile
++++ b/tools/testing/selftests/Makefile
+@@ -4,6 +4,7 @@ TARGETS += efivarfs
+ TARGETS += kcmp
+ TARGETS += memory-hotplug
+ TARGETS += mqueue
++TARGETS += mount
+ TARGETS += net
+ TARGETS += ptrace
+ TARGETS += timers
+diff --git a/tools/testing/selftests/mount/Makefile b/tools/testing/selftests/mount/Makefile
+new file mode 100644
+index 0000000..337d853
+--- /dev/null
++++ b/tools/testing/selftests/mount/Makefile
+@@ -0,0 +1,17 @@
++# Makefile for mount selftests.
++
++all: unprivileged-remount-test
++
++unprivileged-remount-test: unprivileged-remount-test.c
++ gcc -Wall -O2 unprivileged-remount-test.c -o unprivileged-remount-test
++
++# Allow specific tests to be selected.
++test_unprivileged_remount: unprivileged-remount-test
++ @if [ -f /proc/self/uid_map ] ; then ./unprivileged-remount-test ; fi
++
++run_tests: all test_unprivileged_remount
++
++clean:
++ rm -f unprivileged-remount-test
++
++.PHONY: all test_unprivileged_remount
+diff --git a/tools/testing/selftests/mount/unprivileged-remount-test.c b/tools/testing/selftests/mount/unprivileged-remount-test.c
+new file mode 100644
+index 0000000..1b3ff2f
+--- /dev/null
++++ b/tools/testing/selftests/mount/unprivileged-remount-test.c
+@@ -0,0 +1,242 @@
++#define _GNU_SOURCE
++#include <sched.h>
++#include <stdio.h>
++#include <errno.h>
++#include <string.h>
++#include <sys/types.h>
++#include <sys/mount.h>
++#include <sys/wait.h>
++#include <stdlib.h>
++#include <unistd.h>
++#include <fcntl.h>
++#include <grp.h>
++#include <stdbool.h>
++#include <stdarg.h>
++
++#ifndef CLONE_NEWNS
++# define CLONE_NEWNS 0x00020000
++#endif
++#ifndef CLONE_NEWUTS
++# define CLONE_NEWUTS 0x04000000
++#endif
++#ifndef CLONE_NEWIPC
++# define CLONE_NEWIPC 0x08000000
++#endif
++#ifndef CLONE_NEWNET
++# define CLONE_NEWNET 0x40000000
++#endif
++#ifndef CLONE_NEWUSER
++# define CLONE_NEWUSER 0x10000000
++#endif
++#ifndef CLONE_NEWPID
++# define CLONE_NEWPID 0x20000000
++#endif
++
++#ifndef MS_RELATIME
++#define MS_RELATIME (1 << 21)
++#endif
++#ifndef MS_STRICTATIME
++#define MS_STRICTATIME (1 << 24)
++#endif
++
++static void die(char *fmt, ...)
++{
++ va_list ap;
++ va_start(ap, fmt);
++ vfprintf(stderr, fmt, ap);
++ va_end(ap);
++ exit(EXIT_FAILURE);
++}
++
++static void write_file(char *filename, char *fmt, ...)
++{
++ char buf[4096];
++ int fd;
++ ssize_t written;
++ int buf_len;
++ va_list ap;
++
++ va_start(ap, fmt);
++ buf_len = vsnprintf(buf, sizeof(buf), fmt, ap);
++ va_end(ap);
++ if (buf_len < 0) {
++ die("vsnprintf failed: %s\n",
++ strerror(errno));
++ }
++ if (buf_len >= sizeof(buf)) {
++ die("vsnprintf output truncated\n");
++ }
++
++ fd = open(filename, O_WRONLY);
++ if (fd < 0) {
++ die("open of %s failed: %s\n",
++ filename, strerror(errno));
++ }
++ written = write(fd, buf, buf_len);
++ if (written != buf_len) {
++ if (written >= 0) {
++ die("short write to %s\n", filename);
++ } else {
++ die("write to %s failed: %s\n",
++ filename, strerror(errno));
++ }
++ }
++ if (close(fd) != 0) {
++ die("close of %s failed: %s\n",
++ filename, strerror(errno));
++ }
++}
++
++static void create_and_enter_userns(void)
++{
++ uid_t uid;
++ gid_t gid;
++
++ uid = getuid();
++ gid = getgid();
++
++ if (unshare(CLONE_NEWUSER) !=0) {
++ die("unshare(CLONE_NEWUSER) failed: %s\n",
++ strerror(errno));
++ }
++
++ write_file("/proc/self/uid_map", "0 %d 1", uid);
++ write_file("/proc/self/gid_map", "0 %d 1", gid);
++
++ if (setgroups(0, NULL) != 0) {
++ die("setgroups failed: %s\n",
++ strerror(errno));
++ }
++ if (setgid(0) != 0) {
++ die ("setgid(0) failed %s\n",
++ strerror(errno));
++ }
++ if (setuid(0) != 0) {
++ die("setuid(0) failed %s\n",
++ strerror(errno));
++ }
++}
++
++static
++bool test_unpriv_remount(int mount_flags, int remount_flags, int invalid_flags)
++{
++ pid_t child;
++
++ child = fork();
++ if (child == -1) {
++ die("fork failed: %s\n",
++ strerror(errno));
++ }
++ if (child != 0) { /* parent */
++ pid_t pid;
++ int status;
++ pid = waitpid(child, &status, 0);
++ if (pid == -1) {
++ die("waitpid failed: %s\n",
++ strerror(errno));
++ }
++ if (pid != child) {
++ die("waited for %d got %d\n",
++ child, pid);
++ }
++ if (!WIFEXITED(status)) {
++ die("child did not terminate cleanly\n");
++ }
++ return WEXITSTATUS(status) == EXIT_SUCCESS ? true : false;
++ }
++
++ create_and_enter_userns();
++ if (unshare(CLONE_NEWNS) != 0) {
++ die("unshare(CLONE_NEWNS) failed: %s\n",
++ strerror(errno));
++ }
++
++ if (mount("testing", "/tmp", "ramfs", mount_flags, NULL) != 0) {
++ die("mount of /tmp failed: %s\n",
++ strerror(errno));
++ }
++
++ create_and_enter_userns();
++
++ if (unshare(CLONE_NEWNS) != 0) {
++ die("unshare(CLONE_NEWNS) failed: %s\n",
++ strerror(errno));
++ }
++
++ if (mount("/tmp", "/tmp", "none",
++ MS_REMOUNT | MS_BIND | remount_flags, NULL) != 0) {
++ /* system("cat /proc/self/mounts"); */
++ die("remount of /tmp failed: %s\n",
++ strerror(errno));
++ }
++
++ if (mount("/tmp", "/tmp", "none",
++ MS_REMOUNT | MS_BIND | invalid_flags, NULL) == 0) {
++ /* system("cat /proc/self/mounts"); */
++ die("remount of /tmp with invalid flags "
++ "succeeded unexpectedly\n");
++ }
++ exit(EXIT_SUCCESS);
++}
++
++static bool test_unpriv_remount_simple(int mount_flags)
++{
++ return test_unpriv_remount(mount_flags, mount_flags, 0);
++}
++
++static bool test_unpriv_remount_atime(int mount_flags, int invalid_flags)
++{
++ return test_unpriv_remount(mount_flags, mount_flags, invalid_flags);
++}
++
++int main(int argc, char **argv)
++{
++ if (!test_unpriv_remount_simple(MS_RDONLY|MS_NODEV)) {
++ die("MS_RDONLY malfunctions\n");
++ }
++ if (!test_unpriv_remount_simple(MS_NODEV)) {
++ die("MS_NODEV malfunctions\n");
++ }
++ if (!test_unpriv_remount_simple(MS_NOSUID|MS_NODEV)) {
++ die("MS_NOSUID malfunctions\n");
++ }
++ if (!test_unpriv_remount_simple(MS_NOEXEC|MS_NODEV)) {
++ die("MS_NOEXEC malfunctions\n");
++ }
++ if (!test_unpriv_remount_atime(MS_RELATIME|MS_NODEV,
++ MS_NOATIME|MS_NODEV))
++ {
++ die("MS_RELATIME malfunctions\n");
++ }
++ if (!test_unpriv_remount_atime(MS_STRICTATIME|MS_NODEV,
++ MS_NOATIME|MS_NODEV))
++ {
++ die("MS_STRICTATIME malfunctions\n");
++ }
++ if (!test_unpriv_remount_atime(MS_NOATIME|MS_NODEV,
++ MS_STRICTATIME|MS_NODEV))
++ {
++ die("MS_RELATIME malfunctions\n");
++ }
++ if (!test_unpriv_remount_atime(MS_RELATIME|MS_NODIRATIME|MS_NODEV,
++ MS_NOATIME|MS_NODEV))
++ {
++ die("MS_RELATIME malfunctions\n");
++ }
++ if (!test_unpriv_remount_atime(MS_STRICTATIME|MS_NODIRATIME|MS_NODEV,
++ MS_NOATIME|MS_NODEV))
++ {
++ die("MS_RELATIME malfunctions\n");
++ }
++ if (!test_unpriv_remount_atime(MS_NOATIME|MS_NODIRATIME|MS_NODEV,
++ MS_STRICTATIME|MS_NODEV))
++ {
++ die("MS_RELATIME malfunctions\n");
++ }
++ if (!test_unpriv_remount(MS_STRICTATIME|MS_NODEV, MS_NODEV,
++ MS_NOATIME|MS_NODEV))
++ {
++ die("Default atime malfunctions\n");
++ }
++ return EXIT_SUCCESS;
++}
Added: dists/trunk/linux/debian/patches/bugfix/all/mnt-Change-the-default-remount-atime-from-relatime-t.patch
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ dists/trunk/linux/debian/patches/bugfix/all/mnt-Change-the-default-remount-atime-from-relatime-t.patch Sun Sep 7 22:57:20 2014 (r21777)
@@ -0,0 +1,53 @@
+From: "Eric W. Biederman" <ebiederm at xmission.com>
+Date: Mon, 28 Jul 2014 17:36:04 -0700
+Subject: [4/5] mnt: Change the default remount atime from relatime to the
+ existing value
+Origin: https://git.kernel.org/linus/ffbc6f0ead47fa5a1dc9642b0331cb75c20a640e
+
+Since March 2009 the kernel has treated the state that if no
+MS_..ATIME flags are passed then the kernel defaults to relatime.
+
+Defaulting to relatime instead of the existing atime state during a
+remount is silly, and causes problems in practice for people who don't
+specify any MS_...ATIME flags and to get the default filesystem atime
+setting. Those users may encounter a permission error because the
+default atime setting does not work.
+
+A default that does not work and causes permission problems is
+ridiculous, so preserve the existing value to have a default
+atime setting that is always guaranteed to work.
+
+Using the default atime setting in this way is particularly
+interesting for applications built to run in restricted userspace
+environments without /proc mounted, as the existing atime mount
+options of a filesystem can not be read from /proc/mounts.
+
+In practice this fixes user space that uses the default atime
+setting on remount that are broken by the permission checks
+keeping less privileged users from changing more privileged users
+atime settings.
+
+Cc: stable at vger.kernel.org
+Acked-by: Serge E. Hallyn <serge.hallyn at ubuntu.com>
+Signed-off-by: "Eric W. Biederman" <ebiederm at xmission.com>
+---
+ fs/namespace.c | 8 ++++++++
+ 1 file changed, 8 insertions(+)
+
+--- a/fs/namespace.c
++++ b/fs/namespace.c
+@@ -2475,6 +2475,14 @@ long do_mount(const char *dev_name, cons
+ if (flags & MS_RDONLY)
+ mnt_flags |= MNT_READONLY;
+
++ /* The default atime for remount is preservation */
++ if ((flags & MS_REMOUNT) &&
++ ((flags & (MS_NOATIME | MS_NODIRATIME | MS_RELATIME |
++ MS_STRICTATIME)) == 0)) {
++ mnt_flags &= ~MNT_ATIME_MASK;
++ mnt_flags |= path.mnt->mnt_flags & MNT_ATIME_MASK;
++ }
++
+ flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN |
+ MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
+ MS_STRICTATIME);
Added: dists/trunk/linux/debian/patches/bugfix/all/mnt-Correct-permission-checks-in-do_remount.patch
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ dists/trunk/linux/debian/patches/bugfix/all/mnt-Correct-permission-checks-in-do_remount.patch Sun Sep 7 22:57:20 2014 (r21777)
@@ -0,0 +1,125 @@
+From: "Eric W. Biederman" <ebiederm at xmission.com>
+Date: Mon, 28 Jul 2014 17:26:07 -0700
+Subject: [3/5] mnt: Correct permission checks in do_remount
+Origin: https://git.kernel.org/linus/9566d6742852c527bf5af38af5cbb878dad75705
+
+While invesgiating the issue where in "mount --bind -oremount,ro ..."
+would result in later "mount --bind -oremount,rw" succeeding even if
+the mount started off locked I realized that there are several
+additional mount flags that should be locked and are not.
+
+In particular MNT_NOSUID, MNT_NODEV, MNT_NOEXEC, and the atime
+flags in addition to MNT_READONLY should all be locked. These
+flags are all per superblock, can all be changed with MS_BIND,
+and should not be changable if set by a more privileged user.
+
+The following additions to the current logic are added in this patch.
+- nosuid may not be clearable by a less privileged user.
+- nodev may not be clearable by a less privielged user.
+- noexec may not be clearable by a less privileged user.
+- atime flags may not be changeable by a less privileged user.
+
+The logic with atime is that always setting atime on access is a
+global policy and backup software and auditing software could break if
+atime bits are not updated (when they are configured to be updated),
+and serious performance degradation could result (DOS attack) if atime
+updates happen when they have been explicitly disabled. Therefore an
+unprivileged user should not be able to mess with the atime bits set
+by a more privileged user.
+
+The additional restrictions are implemented with the addition of
+MNT_LOCK_NOSUID, MNT_LOCK_NODEV, MNT_LOCK_NOEXEC, and MNT_LOCK_ATIME
+mnt flags.
+
+Taken together these changes and the fixes for MNT_LOCK_READONLY
+should make it safe for an unprivileged user to create a user
+namespace and to call "mount --bind -o remount,... ..." without
+the danger of mount flags being changed maliciously.
+
+Cc: stable at vger.kernel.org
+Acked-by: Serge E. Hallyn <serge.hallyn at ubuntu.com>
+Signed-off-by: "Eric W. Biederman" <ebiederm at xmission.com>
+---
+ fs/namespace.c | 36 +++++++++++++++++++++++++++++++++---
+ include/linux/mount.h | 5 +++++
+ 2 files changed, 38 insertions(+), 3 deletions(-)
+
+--- a/fs/namespace.c
++++ b/fs/namespace.c
+@@ -891,8 +891,21 @@ static struct mount *clone_mnt(struct mo
+
+ mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~(MNT_WRITE_HOLD|MNT_MARKED);
+ /* Don't allow unprivileged users to change mount flags */
+- if ((flag & CL_UNPRIVILEGED) && (mnt->mnt.mnt_flags & MNT_READONLY))
+- mnt->mnt.mnt_flags |= MNT_LOCK_READONLY;
++ if (flag & CL_UNPRIVILEGED) {
++ mnt->mnt.mnt_flags |= MNT_LOCK_ATIME;
++
++ if (mnt->mnt.mnt_flags & MNT_READONLY)
++ mnt->mnt.mnt_flags |= MNT_LOCK_READONLY;
++
++ if (mnt->mnt.mnt_flags & MNT_NODEV)
++ mnt->mnt.mnt_flags |= MNT_LOCK_NODEV;
++
++ if (mnt->mnt.mnt_flags & MNT_NOSUID)
++ mnt->mnt.mnt_flags |= MNT_LOCK_NOSUID;
++
++ if (mnt->mnt.mnt_flags & MNT_NOEXEC)
++ mnt->mnt.mnt_flags |= MNT_LOCK_NOEXEC;
++ }
+
+ /* Don't allow unprivileged users to reveal what is under a mount */
+ if ((flag & CL_UNPRIVILEGED) && list_empty(&old->mnt_expire))
+@@ -1933,6 +1946,23 @@ static int do_remount(struct path *path,
+ !(mnt_flags & MNT_READONLY)) {
+ return -EPERM;
+ }
++ if ((mnt->mnt.mnt_flags & MNT_LOCK_NODEV) &&
++ !(mnt_flags & MNT_NODEV)) {
++ return -EPERM;
++ }
++ if ((mnt->mnt.mnt_flags & MNT_LOCK_NOSUID) &&
++ !(mnt_flags & MNT_NOSUID)) {
++ return -EPERM;
++ }
++ if ((mnt->mnt.mnt_flags & MNT_LOCK_NOEXEC) &&
++ !(mnt_flags & MNT_NOEXEC)) {
++ return -EPERM;
++ }
++ if ((mnt->mnt.mnt_flags & MNT_LOCK_ATIME) &&
++ ((mnt->mnt.mnt_flags & MNT_ATIME_MASK) != (mnt_flags & MNT_ATIME_MASK))) {
++ return -EPERM;
++ }
++
+ err = security_sb_remount(sb, data);
+ if (err)
+ return err;
+@@ -2131,7 +2161,7 @@ static int do_new_mount(struct path *pat
+ */
+ if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) {
+ flags |= MS_NODEV;
+- mnt_flags |= MNT_NODEV;
++ mnt_flags |= MNT_NODEV | MNT_LOCK_NODEV;
+ }
+ }
+
+--- a/include/linux/mount.h
++++ b/include/linux/mount.h
+@@ -45,12 +45,17 @@ struct mnt_namespace;
+ #define MNT_USER_SETTABLE_MASK (MNT_NOSUID | MNT_NODEV | MNT_NOEXEC \
+ | MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME \
+ | MNT_READONLY)
++#define MNT_ATIME_MASK (MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME )
+
+ #define MNT_INTERNAL_FLAGS (MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL | \
+ MNT_DOOMED | MNT_SYNC_UMOUNT | MNT_MARKED)
+
+ #define MNT_INTERNAL 0x4000
+
++#define MNT_LOCK_ATIME 0x040000
++#define MNT_LOCK_NOEXEC 0x080000
++#define MNT_LOCK_NOSUID 0x100000
++#define MNT_LOCK_NODEV 0x200000
+ #define MNT_LOCK_READONLY 0x400000
+ #define MNT_LOCKED 0x800000
+ #define MNT_DOOMED 0x1000000
Added: dists/trunk/linux/debian/patches/bugfix/all/mnt-Move-the-test-for-MNT_LOCK_READONLY-from-change_.patch
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ dists/trunk/linux/debian/patches/bugfix/all/mnt-Move-the-test-for-MNT_LOCK_READONLY-from-change_.patch Sun Sep 7 22:57:20 2014 (r21777)
@@ -0,0 +1,50 @@
+From: "Eric W. Biederman" <ebiederm at xmission.com>
+Date: Mon, 28 Jul 2014 17:10:56 -0700
+Subject: [2/5] mnt: Move the test for MNT_LOCK_READONLY from
+ change_mount_flags into do_remount
+Origin: https://git.kernel.org/linus/07b645589dcda8b7a5249e096fece2a67556f0f4
+
+There are no races as locked mount flags are guaranteed to never change.
+
+Moving the test into do_remount makes it more visible, and ensures all
+filesystem remounts pass the MNT_LOCK_READONLY permission check. This
+second case is not an issue today as filesystem remounts are guarded
+by capable(CAP_DAC_ADMIN) and thus will always fail in less privileged
+mount namespaces, but it could become an issue in the future.
+
+Cc: stable at vger.kernel.org
+Acked-by: Serge E. Hallyn <serge.hallyn at ubuntu.com>
+Signed-off-by: "Eric W. Biederman" <ebiederm at xmission.com>
+---
+ fs/namespace.c | 13 ++++++++++---
+ 1 file changed, 10 insertions(+), 3 deletions(-)
+
+--- a/fs/namespace.c
++++ b/fs/namespace.c
+@@ -1898,9 +1898,6 @@ static int change_mount_flags(struct vfs
+ if (readonly_request == __mnt_is_readonly(mnt))
+ return 0;
+
+- if (mnt->mnt_flags & MNT_LOCK_READONLY)
+- return -EPERM;
+-
+ if (readonly_request)
+ error = mnt_make_readonly(real_mount(mnt));
+ else
+@@ -1926,6 +1923,16 @@ static int do_remount(struct path *path,
+ if (path->dentry != path->mnt->mnt_root)
+ return -EINVAL;
+
++ /* Don't allow changing of locked mnt flags.
++ *
++ * No locks need to be held here while testing the various
++ * MNT_LOCK flags because those flags can never be cleared
++ * once they are set.
++ */
++ if ((mnt->mnt.mnt_flags & MNT_LOCK_READONLY) &&
++ !(mnt_flags & MNT_READONLY)) {
++ return -EPERM;
++ }
+ err = security_sb_remount(sb, data);
+ if (err)
+ return err;
Added: dists/trunk/linux/debian/patches/bugfix/all/mnt-Only-change-user-settable-mount-flags-in-remount.patch
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ dists/trunk/linux/debian/patches/bugfix/all/mnt-Only-change-user-settable-mount-flags-in-remount.patch Sun Sep 7 22:57:20 2014 (r21777)
@@ -0,0 +1,48 @@
+From: "Eric W. Biederman" <ebiederm at xmission.com>
+Date: Mon, 28 Jul 2014 16:26:53 -0700
+Subject: [1/5] mnt: Only change user settable mount flags in remount
+Origin: https://git.kernel.org/linus/a6138db815df5ee542d848318e5dae681590fccd
+
+Kenton Varda <kenton at sandstorm.io> discovered that by remounting a
+read-only bind mount read-only in a user namespace the
+MNT_LOCK_READONLY bit would be cleared, allowing an unprivileged user
+to the remount a read-only mount read-write.
+
+Correct this by replacing the mask of mount flags to preserve
+with a mask of mount flags that may be changed, and preserve
+all others. This ensures that any future bugs with this mask and
+remount will fail in an easy to detect way where new mount flags
+simply won't change.
+
+Cc: stable at vger.kernel.org
+Acked-by: Serge E. Hallyn <serge.hallyn at ubuntu.com>
+Signed-off-by: "Eric W. Biederman" <ebiederm at xmission.com>
+---
+ fs/namespace.c | 2 +-
+ include/linux/mount.h | 4 +++-
+ 2 files changed, 4 insertions(+), 2 deletions(-)
+
+--- a/fs/namespace.c
++++ b/fs/namespace.c
+@@ -1939,7 +1939,7 @@ static int do_remount(struct path *path,
+ err = do_remount_sb(sb, flags, data, 0);
+ if (!err) {
+ lock_mount_hash();
+- mnt_flags |= mnt->mnt.mnt_flags & MNT_PROPAGATION_MASK;
++ mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK;
+ mnt->mnt.mnt_flags = mnt_flags;
+ touch_mnt_namespace(mnt->mnt_ns);
+ unlock_mount_hash();
+--- a/include/linux/mount.h
++++ b/include/linux/mount.h
+@@ -42,7 +42,9 @@ struct mnt_namespace;
+ * flag, consider how it interacts with shared mounts.
+ */
+ #define MNT_SHARED_MASK (MNT_UNBINDABLE)
+-#define MNT_PROPAGATION_MASK (MNT_SHARED | MNT_UNBINDABLE)
++#define MNT_USER_SETTABLE_MASK (MNT_NOSUID | MNT_NODEV | MNT_NOEXEC \
++ | MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME \
++ | MNT_READONLY)
+
+ #define MNT_INTERNAL_FLAGS (MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL | \
+ MNT_DOOMED | MNT_SYNC_UMOUNT | MNT_MARKED)
Modified: dists/trunk/linux/debian/patches/series
==============================================================================
--- dists/trunk/linux/debian/patches/series Sun Sep 7 20:46:18 2014 (r21776)
+++ dists/trunk/linux/debian/patches/series Sun Sep 7 22:57:20 2014 (r21777)
@@ -106,3 +106,8 @@
bugfix/all/aio-fix-reqs_available-handling.patch
features/all/virtio-scsi-Implement-change_queue_depth-for-virtscs.patch
debian/revert-staging-sm7xxfb-remove-driver.patch
+bugfix/all/mnt-Only-change-user-settable-mount-flags-in-remount.patch
+bugfix/all/mnt-Move-the-test-for-MNT_LOCK_READONLY-from-change_.patch
+bugfix/all/mnt-Correct-permission-checks-in-do_remount.patch
+bugfix/all/mnt-Change-the-default-remount-atime-from-relatime-t.patch
+bugfix/all/mnt-Add-tests-for-unprivileged-remount-cases-that-ha.patch
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