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CVE-2014-8989 userns can bypass group restrictions (rhbz 1170684 1170688)

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This commit is contained in:
Josh Boyer 2014-12-18 16:17:32 -05:00
parent 672002c87d
commit 363cd71ff3
14 changed files with 1255 additions and 0 deletions
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90
groups-Consolidate-the-setgroups-permission-checks.patch Normal file
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@ -0,0 +1,90 @@
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Fri, 5 Dec 2014 17:19:27 -0600
Subject: [PATCH] groups: Consolidate the setgroups permission checks
Today there are 3 instances of setgroups and due to an oversight their
permission checking has diverged. Add a common function so that
they may all share the same permission checking code.
This corrects the current oversight in the current permission checks
and adds a helper to avoid this in the future.
A user namespace security fix will update this new helper, shortly.
Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
arch/s390/kernel/compat_linux.c | 2 +-
include/linux/cred.h | 1 +
kernel/groups.c | 9 ++++++++-
kernel/uid16.c | 2 +-
4 files changed, 11 insertions(+), 3 deletions(-)
diff --git a/arch/s390/kernel/compat_linux.c b/arch/s390/kernel/compat_linux.c
index ca38139423ae..437e61159279 100644
--- a/arch/s390/kernel/compat_linux.c
+++ b/arch/s390/kernel/compat_linux.c
@@ -249,7 +249,7 @@ COMPAT_SYSCALL_DEFINE2(s390_setgroups16, int, gidsetsize, u16 __user *, grouplis
struct group_info *group_info;
int retval;
- if (!capable(CAP_SETGID))
+ if (!may_setgroups())
return -EPERM;
if ((unsigned)gidsetsize > NGROUPS_MAX)
return -EINVAL;
diff --git a/include/linux/cred.h b/include/linux/cred.h
index b2d0820837c4..2fb2ca2127ed 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -68,6 +68,7 @@ extern void groups_free(struct group_info *);
extern int set_current_groups(struct group_info *);
extern void set_groups(struct cred *, struct group_info *);
extern int groups_search(const struct group_info *, kgid_t);
+extern bool may_setgroups(void);
/* access the groups "array" with this macro */
#define GROUP_AT(gi, i) \
diff --git a/kernel/groups.c b/kernel/groups.c
index 451698f86cfa..02d8a251c476 100644
--- a/kernel/groups.c
+++ b/kernel/groups.c
@@ -213,6 +213,13 @@ out:
return i;
}
+bool may_setgroups(void)
+{
+ struct user_namespace *user_ns = current_user_ns();
+
+ return ns_capable(user_ns, CAP_SETGID);
+}
+
/*
* SMP: Our groups are copy-on-write. We can set them safely
* without another task interfering.
@@ -223,7 +230,7 @@ SYSCALL_DEFINE2(setgroups, int, gidsetsize, gid_t __user *, grouplist)
struct group_info *group_info;
int retval;
- if (!ns_capable(current_user_ns(), CAP_SETGID))
+ if (!may_setgroups())
return -EPERM;
if ((unsigned)gidsetsize > NGROUPS_MAX)
return -EINVAL;
diff --git a/kernel/uid16.c b/kernel/uid16.c
index 602e5bbbceff..d58cc4d8f0d1 100644
--- a/kernel/uid16.c
+++ b/kernel/uid16.c
@@ -176,7 +176,7 @@ SYSCALL_DEFINE2(setgroups16, int, gidsetsize, old_gid_t __user *, grouplist)
struct group_info *group_info;
int retval;
- if (!ns_capable(current_user_ns(), CAP_SETGID))
+ if (!may_setgroups())
return -EPERM;
if ((unsigned)gidsetsize > NGROUPS_MAX)
return -EINVAL;
--
2.1.0

35
kernel.spec
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@ -645,6 +645,23 @@ Patch26106: dm-cache-fix-spurious-cell_defer-when-dealing-with-p.patch
Patch26107: uapi-linux-target_core_user.h-fix-headers_install.sh.patch
#mount fixes for stable
Patch26108: mnt-Implicitly-add-MNT_NODEV-on-remount-when-it-was-.patch
Patch26109: mnt-Update-unprivileged-remount-test.patch
Patch26110: umount-Disallow-unprivileged-mount-force.patch
#CVE-2014-8989 rhbz 1170684 1170688
Patch26111: groups-Consolidate-the-setgroups-permission-checks.patch
Patch26112: userns-Document-what-the-invariant-required-for-safe.patch
Patch26113: userns-Don-t-allow-setgroups-until-a-gid-mapping-has.patch
Patch26114: userns-Don-t-allow-unprivileged-creation-of-gid-mapp.patch
Patch26115: userns-Check-euid-no-fsuid-when-establishing-an-unpr.patch
Patch26116: userns-Only-allow-the-creator-of-the-userns-unprivil.patch
Patch26117: userns-Rename-id_map_mutex-to-userns_state_mutex.patch
Patch26118: userns-Add-a-knob-to-disable-setgroups-on-a-per-user.patch
Patch26119: userns-Allow-setting-gid_maps-without-privilege-when.patch
Patch26120: userns-Unbreak-the-unprivileged-remount-tests.patch
# git clone ssh://git.fedorahosted.org/git/kernel-arm64.git, git diff master...devel
Patch30000: kernel-arm64.patch
@ -1398,6 +1415,23 @@ ApplyPatch dm-cache-fix-spurious-cell_defer-when-dealing-with-p.patch
ApplyPatch uapi-linux-target_core_user.h-fix-headers_install.sh.patch
#mount fixes for stable
ApplyPatch mnt-Implicitly-add-MNT_NODEV-on-remount-when-it-was-.patch
ApplyPatch mnt-Update-unprivileged-remount-test.patch
ApplyPatch umount-Disallow-unprivileged-mount-force.patch
#CVE-2014-8989 rhbz 1170684 1170688
ApplyPatch groups-Consolidate-the-setgroups-permission-checks.patch
ApplyPatch userns-Document-what-the-invariant-required-for-safe.patch
ApplyPatch userns-Don-t-allow-setgroups-until-a-gid-mapping-has.patch
ApplyPatch userns-Don-t-allow-unprivileged-creation-of-gid-mapp.patch
ApplyPatch userns-Check-euid-no-fsuid-when-establishing-an-unpr.patch
ApplyPatch userns-Only-allow-the-creator-of-the-userns-unprivil.patch
ApplyPatch userns-Rename-id_map_mutex-to-userns_state_mutex.patch
ApplyPatch userns-Add-a-knob-to-disable-setgroups-on-a-per-user.patch
ApplyPatch userns-Allow-setting-gid_maps-without-privilege-when.patch
ApplyPatch userns-Unbreak-the-unprivileged-remount-tests.patch
%if 0%{?aarch64patches}
ApplyPatch kernel-arm64.patch
%ifnarch aarch64 # this is stupid, but i want to notice before secondary koji does.
@ -2267,6 +2301,7 @@ fi
# || ||
%changelog
* Thu Dec 18 2014 Josh Boyer <jwboyer@fedoraproject.org>
- CVE-2014-8989 userns can bypass group restrictions (rhbz 1170684 1170688)
- Fix from Kyle McMartin for target_core_user uapi issue since it's enabled
- Fix dm-cache crash (rhbz 1168434)
- Fix blk-mq crash on CPU hotplug (rhbz 1175261)

41
mnt-Implicitly-add-MNT_NODEV-on-remount-when-it-was-.patch Normal file
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@ -0,0 +1,41 @@
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Wed, 13 Aug 2014 01:33:38 -0700
Subject: [PATCH] mnt: Implicitly add MNT_NODEV on remount when it was
implicitly added by mount
Now that remount is properly enforcing the rule that you can't remove
nodev at least sandstorm.io is breaking when performing a remount.
It turns out that there is an easy intuitive solution implicitly
add nodev on remount when nodev was implicitly added on mount.
Tested-by: Cedric Bosdonnat <cbosdonnat@suse.com>
Tested-by: Richard Weinberger <richard@nod.at>
Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
fs/namespace.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index 5b66b2b3624d..3a1a87dc33df 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2098,7 +2098,13 @@ static int do_remount(struct path *path, int flags, int mnt_flags,
}
if ((mnt->mnt.mnt_flags & MNT_LOCK_NODEV) &&
!(mnt_flags & MNT_NODEV)) {
- return -EPERM;
+ /* Was the nodev implicitly added in mount? */
+ if ((mnt->mnt_ns->user_ns != &init_user_ns) &&
+ !(sb->s_type->fs_flags & FS_USERNS_DEV_MOUNT)) {
+ mnt_flags |= MNT_NODEV;
+ } else {
+ return -EPERM;
+ }
}
if ((mnt->mnt.mnt_flags & MNT_LOCK_NOSUID) &&
!(mnt_flags & MNT_NOSUID)) {
--
2.1.0

280
mnt-Update-unprivileged-remount-test.patch Normal file
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@ -0,0 +1,280 @@
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Fri, 22 Aug 2014 16:39:03 -0500
Subject: [PATCH] mnt: Update unprivileged remount test
- MNT_NODEV should be irrelevant except when reading back mount flags,
no longer specify MNT_NODEV on remount.
- Test MNT_NODEV on devpts where it is meaningful even for unprivileged mounts.
- Add a test to verify that remount of a prexisting mount with the same flags
is allowed and does not change those flags.
- Cleanup up the definitions of MS_REC, MS_RELATIME, MS_STRICTATIME that are used
when the code is built in an environment without them.
- Correct the test error messages when tests fail. There were not 5 tests
that tested MS_RELATIME.
Cc: stable@vger.kernel.org
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---
.../selftests/mount/unprivileged-remount-test.c | 172 +++++++++++++++++----
1 file changed, 142 insertions(+), 30 deletions(-)
diff --git a/tools/testing/selftests/mount/unprivileged-remount-test.c b/tools/testing/selftests/mount/unprivileged-remount-test.c
index 1b3ff2fda4d0..9669d375625a 100644
--- a/tools/testing/selftests/mount/unprivileged-remount-test.c
+++ b/tools/testing/selftests/mount/unprivileged-remount-test.c
@@ -6,6 +6,8 @@
#include <sys/types.h>
#include <sys/mount.h>
#include <sys/wait.h>
+#include <sys/vfs.h>
+#include <sys/statvfs.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
@@ -32,11 +34,14 @@
# define CLONE_NEWPID 0x20000000
#endif
+#ifndef MS_REC
+# define MS_REC 16384
+#endif
#ifndef MS_RELATIME
-#define MS_RELATIME (1 << 21)
+# define MS_RELATIME (1 << 21)
#endif
#ifndef MS_STRICTATIME
-#define MS_STRICTATIME (1 << 24)
+# define MS_STRICTATIME (1 << 24)
#endif
static void die(char *fmt, ...)
@@ -87,6 +92,45 @@ static void write_file(char *filename, char *fmt, ...)
}
}
+static int read_mnt_flags(const char *path)
+{
+ int ret;
+ struct statvfs stat;
+ int mnt_flags;
+
+ ret = statvfs(path, &stat);
+ if (ret != 0) {
+ die("statvfs of %s failed: %s\n",
+ path, strerror(errno));
+ }
+ if (stat.f_flag & ~(ST_RDONLY | ST_NOSUID | ST_NODEV | \
+ ST_NOEXEC | ST_NOATIME | ST_NODIRATIME | ST_RELATIME | \
+ ST_SYNCHRONOUS | ST_MANDLOCK)) {
+ die("Unrecognized mount flags\n");
+ }
+ mnt_flags = 0;
+ if (stat.f_flag & ST_RDONLY)
+ mnt_flags |= MS_RDONLY;
+ if (stat.f_flag & ST_NOSUID)
+ mnt_flags |= MS_NOSUID;
+ if (stat.f_flag & ST_NODEV)
+ mnt_flags |= MS_NODEV;
+ if (stat.f_flag & ST_NOEXEC)
+ mnt_flags |= MS_NOEXEC;
+ if (stat.f_flag & ST_NOATIME)
+ mnt_flags |= MS_NOATIME;
+ if (stat.f_flag & ST_NODIRATIME)
+ mnt_flags |= MS_NODIRATIME;
+ if (stat.f_flag & ST_RELATIME)
+ mnt_flags |= MS_RELATIME;
+ if (stat.f_flag & ST_SYNCHRONOUS)
+ mnt_flags |= MS_SYNCHRONOUS;
+ if (stat.f_flag & ST_MANDLOCK)
+ mnt_flags |= ST_MANDLOCK;
+
+ return mnt_flags;
+}
+
static void create_and_enter_userns(void)
{
uid_t uid;
@@ -118,7 +162,8 @@ static void create_and_enter_userns(void)
}
static
-bool test_unpriv_remount(int mount_flags, int remount_flags, int invalid_flags)
+bool test_unpriv_remount(const char *fstype, const char *mount_options,
+ int mount_flags, int remount_flags, int invalid_flags)
{
pid_t child;
@@ -151,9 +196,11 @@ bool test_unpriv_remount(int mount_flags, int remount_flags, int invalid_flags)
strerror(errno));
}
- if (mount("testing", "/tmp", "ramfs", mount_flags, NULL) != 0) {
- die("mount of /tmp failed: %s\n",
- strerror(errno));
+ if (mount("testing", "/tmp", fstype, mount_flags, mount_options) != 0) {
+ die("mount of %s with options '%s' on /tmp failed: %s\n",
+ fstype,
+ mount_options? mount_options : "",
+ strerror(errno));
}
create_and_enter_userns();
@@ -181,62 +228,127 @@ bool test_unpriv_remount(int mount_flags, int remount_flags, int invalid_flags)
static bool test_unpriv_remount_simple(int mount_flags)
{
- return test_unpriv_remount(mount_flags, mount_flags, 0);
+ return test_unpriv_remount("ramfs", NULL, 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);
+ return test_unpriv_remount("ramfs", NULL, mount_flags, mount_flags,
+ invalid_flags);
+}
+
+static bool test_priv_mount_unpriv_remount(void)
+{
+ pid_t child;
+ int ret;
+ const char *orig_path = "/dev";
+ const char *dest_path = "/tmp";
+ int orig_mnt_flags, remount_mnt_flags;
+
+ 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;
+ }
+
+ orig_mnt_flags = read_mnt_flags(orig_path);
+
+ create_and_enter_userns();
+ ret = unshare(CLONE_NEWNS);
+ if (ret != 0) {
+ die("unshare(CLONE_NEWNS) failed: %s\n",
+ strerror(errno));
+ }
+
+ ret = mount(orig_path, dest_path, "bind", MS_BIND | MS_REC, NULL);
+ if (ret != 0) {
+ die("recursive bind mount of %s onto %s failed: %s\n",
+ orig_path, dest_path, strerror(errno));
+ }
+
+ ret = mount(dest_path, dest_path, "none",
+ MS_REMOUNT | MS_BIND | orig_mnt_flags , NULL);
+ if (ret != 0) {
+ /* system("cat /proc/self/mounts"); */
+ die("remount of /tmp failed: %s\n",
+ strerror(errno));
+ }
+
+ remount_mnt_flags = read_mnt_flags(dest_path);
+ if (orig_mnt_flags != remount_mnt_flags) {
+ die("Mount flags unexpectedly changed during remount of %s originally mounted on %s\n",
+ dest_path, orig_path);
+ }
+ exit(EXIT_SUCCESS);
}
int main(int argc, char **argv)
{
- if (!test_unpriv_remount_simple(MS_RDONLY|MS_NODEV)) {
+ if (!test_unpriv_remount_simple(MS_RDONLY)) {
die("MS_RDONLY malfunctions\n");
}
- if (!test_unpriv_remount_simple(MS_NODEV)) {
+ if (!test_unpriv_remount("devpts", "newinstance", MS_NODEV, MS_NODEV, 0)) {
die("MS_NODEV malfunctions\n");
}
- if (!test_unpriv_remount_simple(MS_NOSUID|MS_NODEV)) {
+ if (!test_unpriv_remount_simple(MS_NOSUID)) {
die("MS_NOSUID malfunctions\n");
}
- if (!test_unpriv_remount_simple(MS_NOEXEC|MS_NODEV)) {
+ if (!test_unpriv_remount_simple(MS_NOEXEC)) {
die("MS_NOEXEC malfunctions\n");
}
- if (!test_unpriv_remount_atime(MS_RELATIME|MS_NODEV,
- MS_NOATIME|MS_NODEV))
+ if (!test_unpriv_remount_atime(MS_RELATIME,
+ MS_NOATIME))
{
die("MS_RELATIME malfunctions\n");
}
- if (!test_unpriv_remount_atime(MS_STRICTATIME|MS_NODEV,
- MS_NOATIME|MS_NODEV))
+ if (!test_unpriv_remount_atime(MS_STRICTATIME,
+ MS_NOATIME))
{
die("MS_STRICTATIME malfunctions\n");
}
- if (!test_unpriv_remount_atime(MS_NOATIME|MS_NODEV,
- MS_STRICTATIME|MS_NODEV))
+ if (!test_unpriv_remount_atime(MS_NOATIME,
+ MS_STRICTATIME))
{
- die("MS_RELATIME malfunctions\n");
+ die("MS_NOATIME malfunctions\n");
}
- if (!test_unpriv_remount_atime(MS_RELATIME|MS_NODIRATIME|MS_NODEV,
- MS_NOATIME|MS_NODEV))
+ if (!test_unpriv_remount_atime(MS_RELATIME|MS_NODIRATIME,
+ MS_NOATIME))
{
- die("MS_RELATIME malfunctions\n");
+ die("MS_RELATIME|MS_NODIRATIME malfunctions\n");
}
- if (!test_unpriv_remount_atime(MS_STRICTATIME|MS_NODIRATIME|MS_NODEV,
- MS_NOATIME|MS_NODEV))
+ if (!test_unpriv_remount_atime(MS_STRICTATIME|MS_NODIRATIME,
+ MS_NOATIME))
{
- die("MS_RELATIME malfunctions\n");
+ die("MS_STRICTATIME|MS_NODIRATIME malfunctions\n");
}
- if (!test_unpriv_remount_atime(MS_NOATIME|MS_NODIRATIME|MS_NODEV,
- MS_STRICTATIME|MS_NODEV))
+ if (!test_unpriv_remount_atime(MS_NOATIME|MS_NODIRATIME,
+ MS_STRICTATIME))
{
- die("MS_RELATIME malfunctions\n");
+ die("MS_NOATIME|MS_DIRATIME malfunctions\n");
}
- if (!test_unpriv_remount(MS_STRICTATIME|MS_NODEV, MS_NODEV,
- MS_NOATIME|MS_NODEV))
+ if (!test_unpriv_remount("ramfs", NULL, MS_STRICTATIME, 0, MS_NOATIME))
{
die("Default atime malfunctions\n");
}
+ if (!test_priv_mount_unpriv_remount()) {
+ die("Mount flags unexpectedly changed after remount\n");
+ }
return EXIT_SUCCESS;
}
--
2.1.0

33
umount-Disallow-unprivileged-mount-force.patch Normal file
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@ -0,0 +1,33 @@
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Sat, 4 Oct 2014 14:44:03 -0700
Subject: [PATCH] umount: Disallow unprivileged mount force
Forced unmount affects not just the mount namespace but the underlying
superblock as well. Restrict forced unmount to the global root user
for now. Otherwise it becomes possible a user in a less privileged
mount namespace to force the shutdown of a superblock of a filesystem
in a more privileged mount namespace, allowing a DOS attack on root.
Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
fs/namespace.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/fs/namespace.c b/fs/namespace.c
index 3a1a87dc33df..43b16af8af30 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1544,6 +1544,9 @@ SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
goto dput_and_out;
if (mnt->mnt.mnt_flags & MNT_LOCKED)
goto dput_and_out;
+ retval = -EPERM;
+ if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN))
+ goto dput_and_out;
retval = do_umount(mnt, flags);
dput_and_out:
--
2.1.0

280
userns-Add-a-knob-to-disable-setgroups-on-a-per-user.patch Normal file
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@ -0,0 +1,280 @@
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Tue, 2 Dec 2014 12:27:26 -0600
Subject: [PATCH] userns: Add a knob to disable setgroups on a per user
namespace basis
- Expose the knob to user space through a proc file /proc/<pid>/setgroups
A value of "deny" means the setgroups system call is disabled in the
current processes user namespace and can not be enabled in the
future in this user namespace.
A value of "allow" means the segtoups system call is enabled.
- Descendant user namespaces inherit the value of setgroups from
their parents.
- A proc file is used (instead of a sysctl) as sysctls currently do
not allow checking the permissions at open time.
- Writing to the proc file is restricted to before the gid_map
for the user namespace is set.
This ensures that disabling setgroups at a user namespace
level will never remove the ability to call setgroups
from a process that already has that ability.
A process may opt in to the setgroups disable for itself by
creating, entering and configuring a user namespace or by calling
setns on an existing user namespace with setgroups disabled.
Processes without privileges already can not call setgroups so this
is a noop. Prodcess with privilege become processes without
privilege when entering a user namespace and as with any other path
to dropping privilege they would not have the ability to call
setgroups. So this remains within the bounds of what is possible
without a knob to disable setgroups permanently in a user namespace.
Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
fs/proc/base.c | 53 ++++++++++++++++++++++++++
include/linux/user_namespace.h | 7 ++++
kernel/user.c | 1 +
kernel/user_namespace.c | 85 ++++++++++++++++++++++++++++++++++++++++++
4 files changed, 146 insertions(+)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 772efa45a452..7dc3ea89ef1a 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2464,6 +2464,57 @@ static const struct file_operations proc_projid_map_operations = {
.llseek = seq_lseek,
.release = proc_id_map_release,
};
+
+static int proc_setgroups_open(struct inode *inode, struct file *file)
+{
+ struct user_namespace *ns = NULL;
+ struct task_struct *task;
+ int ret;
+
+ ret = -ESRCH;
+ task = get_proc_task(inode);
+ if (task) {
+ rcu_read_lock();
+ ns = get_user_ns(task_cred_xxx(task, user_ns));
+ rcu_read_unlock();
+ put_task_struct(task);
+ }
+ if (!ns)
+ goto err;
+
+ if (file->f_mode & FMODE_WRITE) {
+ ret = -EACCES;
+ if (!ns_capable(ns, CAP_SYS_ADMIN))
+ goto err_put_ns;
+ }
+
+ ret = single_open(file, &proc_setgroups_show, ns);
+ if (ret)
+ goto err_put_ns;
+
+ return 0;
+err_put_ns:
+ put_user_ns(ns);
+err:
+ return ret;
+}
+
+static int proc_setgroups_release(struct inode *inode, struct file *file)
+{
+ struct seq_file *seq = file->private_data;
+ struct user_namespace *ns = seq->private;
+ int ret = single_release(inode, file);
+ put_user_ns(ns);
+ return ret;
+}
+
+static const struct file_operations proc_setgroups_operations = {
+ .open = proc_setgroups_open,
+ .write = proc_setgroups_write,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = proc_setgroups_release,
+};
#endif /* CONFIG_USER_NS */
static int proc_pid_personality(struct seq_file *m, struct pid_namespace *ns,
@@ -2572,6 +2623,7 @@ static const struct pid_entry tgid_base_stuff[] = {
REG("uid_map", S_IRUGO|S_IWUSR, proc_uid_map_operations),
REG("gid_map", S_IRUGO|S_IWUSR, proc_gid_map_operations),
REG("projid_map", S_IRUGO|S_IWUSR, proc_projid_map_operations),
+ REG("setgroups", S_IRUGO|S_IWUSR, proc_setgroups_operations),
#endif
#ifdef CONFIG_CHECKPOINT_RESTORE
REG("timers", S_IRUGO, proc_timers_operations),
@@ -2913,6 +2965,7 @@ static const struct pid_entry tid_base_stuff[] = {
REG("uid_map", S_IRUGO|S_IWUSR, proc_uid_map_operations),
REG("gid_map", S_IRUGO|S_IWUSR, proc_gid_map_operations),
REG("projid_map", S_IRUGO|S_IWUSR, proc_projid_map_operations),
+ REG("setgroups", S_IRUGO|S_IWUSR, proc_setgroups_operations),
#endif
};
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 8d493083486a..9f3579ff543d 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -17,6 +17,10 @@ struct uid_gid_map { /* 64 bytes -- 1 cache line */
} extent[UID_GID_MAP_MAX_EXTENTS];
};
+#define USERNS_SETGROUPS_ALLOWED 1UL
+
+#define USERNS_INIT_FLAGS USERNS_SETGROUPS_ALLOWED
+
struct user_namespace {
struct uid_gid_map uid_map;
struct uid_gid_map gid_map;
@@ -27,6 +31,7 @@ struct user_namespace {
kuid_t owner;
kgid_t group;
unsigned int proc_inum;
+ unsigned long flags;
/* Register of per-UID persistent keyrings for this namespace */
#ifdef CONFIG_PERSISTENT_KEYRINGS
@@ -63,6 +68,8 @@ extern const struct seq_operations proc_projid_seq_operations;
extern ssize_t proc_uid_map_write(struct file *, const char __user *, size_t, loff_t *);
extern ssize_t proc_gid_map_write(struct file *, const char __user *, size_t, loff_t *);
extern ssize_t proc_projid_map_write(struct file *, const char __user *, size_t, loff_t *);
+extern ssize_t proc_setgroups_write(struct file *, const char __user *, size_t, loff_t *);
+extern int proc_setgroups_show(struct seq_file *m, void *v);
extern bool userns_may_setgroups(const struct user_namespace *ns);
#else
diff --git a/kernel/user.c b/kernel/user.c
index 4efa39350e44..2d09940c9632 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -51,6 +51,7 @@ struct user_namespace init_user_ns = {
.owner = GLOBAL_ROOT_UID,
.group = GLOBAL_ROOT_GID,
.proc_inum = PROC_USER_INIT_INO,
+ .flags = USERNS_INIT_FLAGS,
#ifdef CONFIG_PERSISTENT_KEYRINGS
.persistent_keyring_register_sem =
__RWSEM_INITIALIZER(init_user_ns.persistent_keyring_register_sem),
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 44a555ac6104..6e80f4c1322b 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -100,6 +100,11 @@ int create_user_ns(struct cred *new)
ns->owner = owner;
ns->group = group;
+ /* Inherit USERNS_SETGROUPS_ALLOWED from our parent */
+ mutex_lock(&userns_state_mutex);
+ ns->flags = parent_ns->flags;
+ mutex_unlock(&userns_state_mutex);
+
set_cred_user_ns(new, ns);
#ifdef CONFIG_PERSISTENT_KEYRINGS
@@ -839,6 +844,84 @@ static bool new_idmap_permitted(const struct file *file,
return false;
}
+int proc_setgroups_show(struct seq_file *seq, void *v)
+{
+ struct user_namespace *ns = seq->private;
+ unsigned long userns_flags = ACCESS_ONCE(ns->flags);
+
+ seq_printf(seq, "%s\n",
+ (userns_flags & USERNS_SETGROUPS_ALLOWED) ?
+ "allow" : "deny");
+ return 0;
+}
+
+ssize_t proc_setgroups_write(struct file *file, const char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ struct seq_file *seq = file->private_data;
+ struct user_namespace *ns = seq->private;
+ char kbuf[8], *pos;
+ bool setgroups_allowed;
+ ssize_t ret;
+
+ /* Only allow a very narrow range of strings to be written */
+ ret = -EINVAL;
+ if ((*ppos != 0) || (count >= sizeof(kbuf)))
+ goto out;
+
+ /* What was written? */
+ ret = -EFAULT;
+ if (copy_from_user(kbuf, buf, count))
+ goto out;
+ kbuf[count] = '\0';
+ pos = kbuf;
+
+ /* What is being requested? */
+ ret = -EINVAL;
+ if (strncmp(pos, "allow", 5) == 0) {
+ pos += 5;
+ setgroups_allowed = true;
+ }
+ else if (strncmp(pos, "deny", 4) == 0) {
+ pos += 4;
+ setgroups_allowed = false;
+ }
+ else
+ goto out;
+
+ /* Verify there is not trailing junk on the line */
+ pos = skip_spaces(pos);
+ if (*pos != '\0')
+ goto out;
+
+ ret = -EPERM;
+ mutex_lock(&userns_state_mutex);
+ if (setgroups_allowed) {
+ /* Enabling setgroups after setgroups has been disabled
+ * is not allowed.
+ */
+ if (!(ns->flags & USERNS_SETGROUPS_ALLOWED))
+ goto out_unlock;
+ } else {
+ /* Permanently disabling setgroups after setgroups has
+ * been enabled by writing the gid_map is not allowed.
+ */
+ if (ns->gid_map.nr_extents != 0)
+ goto out_unlock;
+ ns->flags &= ~USERNS_SETGROUPS_ALLOWED;
+ }
+ mutex_unlock(&userns_state_mutex);
+
+ /* Report a successful write */
+ *ppos = count;
+ ret = count;
+out:
+ return ret;
+out_unlock:
+ mutex_unlock(&userns_state_mutex);
+ goto out;
+}
+
bool userns_may_setgroups(const struct user_namespace *ns)
{
bool allowed;
@@ -848,6 +931,8 @@ bool userns_may_setgroups(const struct user_namespace *ns)
* the user namespace has been established.
*/
allowed = ns->gid_map.nr_extents != 0;
+ /* Is setgroups allowed? */
+ allowed = allowed && (ns->flags & USERNS_SETGROUPS_ALLOWED);
mutex_unlock(&userns_state_mutex);
return allowed;
--
2.1.0

40
userns-Allow-setting-gid_maps-without-privilege-when.patch Normal file
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@ -0,0 +1,40 @@
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Fri, 5 Dec 2014 19:36:04 -0600
Subject: [PATCH] userns: Allow setting gid_maps without privilege when
setgroups is disabled
Now that setgroups can be disabled and not reenabled, setting gid_map
without privielge can now be enabled when setgroups is disabled.
This restores most of the functionality that was lost when unprivileged
setting of gid_map was removed. Applications that use this functionality
will need to check to see if they use setgroups or init_groups, and if they
don't they can be fixed by simply disabling setgroups before writing to
gid_map.
Cc: stable@vger.kernel.org
Reviewed-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
kernel/user_namespace.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 6e80f4c1322b..a2e37c5d2f63 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -826,6 +826,11 @@ static bool new_idmap_permitted(const struct file *file,
kuid_t uid = make_kuid(ns->parent, id);
if (uid_eq(uid, cred->euid))
return true;
+ } else if (cap_setid == CAP_SETGID) {
+ kgid_t gid = make_kgid(ns->parent, id);
+ if (!(ns->flags & USERNS_SETGROUPS_ALLOWED) &&
+ gid_eq(gid, cred->egid))
+ return true;
}
}
--
2.1.0

39
userns-Check-euid-no-fsuid-when-establishing-an-unpr.patch Normal file
View File

@ -0,0 +1,39 @@
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Fri, 5 Dec 2014 18:26:30 -0600
Subject: [PATCH] userns: Check euid no fsuid when establishing an unprivileged
uid mapping
setresuid allows the euid to be set to any of uid, euid, suid, and
fsuid. Therefor it is safe to allow an unprivileged user to map
their euid and use CAP_SETUID privileged with exactly that uid,
as no new credentials can be obtained.
I can not find a combination of existing system calls that allows setting
uid, euid, suid, and fsuid from the fsuid making the previous use
of fsuid for allowing unprivileged mappings a bug.
This is part of a fix for CVE-2014-8989.
Cc: stable@vger.kernel.org
Reviewed-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
kernel/user_namespace.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 1ce6d67c07b7..9451b12a9b6c 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -819,7 +819,7 @@ static bool new_idmap_permitted(const struct file *file,
u32 id = new_map->extent[0].lower_first;
if (cap_setid == CAP_SETUID) {
kuid_t uid = make_kuid(ns->parent, id);
- if (uid_eq(uid, file->f_cred->fsuid))
+ if (uid_eq(uid, file->f_cred->euid))
return true;
}
}
--
2.1.0

48
userns-Document-what-the-invariant-required-for-safe.patch Normal file
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@ -0,0 +1,48 @@
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Fri, 5 Dec 2014 17:51:47 -0600
Subject: [PATCH] userns: Document what the invariant required for safe
unprivileged mappings.
The rule is simple. Don't allow anything that wouldn't be allowed
without unprivileged mappings.
It was previously overlooked that establishing gid mappings would
allow dropping groups and potentially gaining permission to files and
directories that had lesser permissions for a specific group than for
all other users.
This is the rule needed to fix CVE-2014-8989 and prevent any other
security issues with new_idmap_permitted.
The reason for this rule is that the unix permission model is old and
there are programs out there somewhere that take advantage of every
little corner of it. So allowing a uid or gid mapping to be
established without privielge that would allow anything that would not
be allowed without that mapping will result in expectations from some
code somewhere being violated. Violated expectations about the
behavior of the OS is a long way to say a security issue.
Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
kernel/user_namespace.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index aa312b0dc3ec..b99c862a2e3f 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -812,7 +812,9 @@ static bool new_idmap_permitted(const struct file *file,
struct user_namespace *ns, int cap_setid,
struct uid_gid_map *new_map)
{
- /* Allow mapping to your own filesystem ids */
+ /* Don't allow mappings that would allow anything that wouldn't
+ * be allowed without the establishment of unprivileged mappings.
+ */
if ((new_map->nr_extents == 1) && (new_map->extent[0].count == 1)) {
u32 id = new_map->extent[0].lower_first;
if (cap_setid == CAP_SETUID) {
--
2.1.0

98
userns-Don-t-allow-setgroups-until-a-gid-mapping-has.patch Normal file
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@ -0,0 +1,98 @@
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Fri, 5 Dec 2014 18:01:11 -0600
Subject: [PATCH] userns: Don't allow setgroups until a gid mapping has been
setablished
setgroups is unique in not needing a valid mapping before it can be called,
in the case of setgroups(0, NULL) which drops all supplemental groups.
The design of the user namespace assumes that CAP_SETGID can not actually
be used until a gid mapping is established. Therefore add a helper function
to see if the user namespace gid mapping has been established and call
that function in the setgroups permission check.
This is part of the fix for CVE-2014-8989, being able to drop groups
without privilege using user namespaces.
Cc: stable@vger.kernel.org
Reviewed-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
include/linux/user_namespace.h | 5 +++++
kernel/groups.c | 4 +++-
kernel/user_namespace.c | 14 ++++++++++++++
3 files changed, 22 insertions(+), 1 deletion(-)
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index e95372654f09..8d493083486a 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -63,6 +63,7 @@ extern const struct seq_operations proc_projid_seq_operations;
extern ssize_t proc_uid_map_write(struct file *, const char __user *, size_t, loff_t *);
extern ssize_t proc_gid_map_write(struct file *, const char __user *, size_t, loff_t *);
extern ssize_t proc_projid_map_write(struct file *, const char __user *, size_t, loff_t *);
+extern bool userns_may_setgroups(const struct user_namespace *ns);
#else
static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
@@ -87,6 +88,10 @@ static inline void put_user_ns(struct user_namespace *ns)
{
}
+static inline bool userns_may_setgroups(const struct user_namespace *ns)
+{
+ return true;
+}
#endif
#endif /* _LINUX_USER_H */
diff --git a/kernel/groups.c b/kernel/groups.c
index 02d8a251c476..664411f171b5 100644
--- a/kernel/groups.c
+++ b/kernel/groups.c
@@ -6,6 +6,7 @@
#include <linux/slab.h>
#include <linux/security.h>
#include <linux/syscalls.h>
+#include <linux/user_namespace.h>
#include <asm/uaccess.h>
/* init to 2 - one for init_task, one to ensure it is never freed */
@@ -217,7 +218,8 @@ bool may_setgroups(void)
{
struct user_namespace *user_ns = current_user_ns();
- return ns_capable(user_ns, CAP_SETGID);
+ return ns_capable(user_ns, CAP_SETGID) &&
+ userns_may_setgroups(user_ns);
}
/*
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index b99c862a2e3f..27c8dab48c07 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -843,6 +843,20 @@ static bool new_idmap_permitted(const struct file *file,
return false;
}
+bool userns_may_setgroups(const struct user_namespace *ns)
+{
+ bool allowed;
+
+ mutex_lock(&id_map_mutex);
+ /* It is not safe to use setgroups until a gid mapping in
+ * the user namespace has been established.
+ */
+ allowed = ns->gid_map.nr_extents != 0;
+ mutex_unlock(&id_map_mutex);
+
+ return allowed;
+}
+
static void *userns_get(struct task_struct *task)
{
struct user_namespace *user_ns;
--
2.1.0

46
userns-Don-t-allow-unprivileged-creation-of-gid-mapp.patch Normal file
View File

@ -0,0 +1,46 @@
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Fri, 5 Dec 2014 18:14:19 -0600
Subject: [PATCH] userns: Don't allow unprivileged creation of gid mappings
As any gid mapping will allow and must allow for backwards
compatibility dropping groups don't allow any gid mappings to be
established without CAP_SETGID in the parent user namespace.
For a small class of applications this change breaks userspace
and removes useful functionality. This small class of applications
includes tools/testing/selftests/mount/unprivilged-remount-test.c
Most of the removed functionality will be added back with the addition
of a one way knob to disable setgroups. Once setgroups is disabled
setting the gid_map becomes as safe as setting the uid_map.
For more common applications that set the uid_map and the gid_map
with privilege this change will have no affect.
This is part of a fix for CVE-2014-8989.
Cc: stable@vger.kernel.org
Reviewed-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
kernel/user_namespace.c | 4 ----
1 file changed, 4 deletions(-)
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 27c8dab48c07..1ce6d67c07b7 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -821,10 +821,6 @@ static bool new_idmap_permitted(const struct file *file,
kuid_t uid = make_kuid(ns->parent, id);
if (uid_eq(uid, file->f_cred->fsuid))
return true;
- } else if (cap_setid == CAP_SETGID) {
- kgid_t gid = make_kgid(ns->parent, id);
- if (gid_eq(gid, file->f_cred->fsgid))
- return true;
}
}
--
2.1.0

54
userns-Only-allow-the-creator-of-the-userns-unprivil.patch Normal file
View File

@ -0,0 +1,54 @@
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Wed, 26 Nov 2014 23:22:14 -0600
Subject: [PATCH] userns: Only allow the creator of the userns unprivileged
mappings
If you did not create the user namespace and are allowed
to write to uid_map or gid_map you should already have the necessary
privilege in the parent user namespace to establish any mapping
you want so this will not affect userspace in practice.
Limiting unprivileged uid mapping establishment to the creator of the
user namespace makes it easier to verify all credentials obtained with
the uid mapping can be obtained without the uid mapping without
privilege.
Limiting unprivileged gid mapping establishment (which is temporarily
absent) to the creator of the user namespace also ensures that the
combination of uid and gid can already be obtained without privilege.
This is part of the fix for CVE-2014-8989.
Cc: stable@vger.kernel.org
Reviewed-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
kernel/user_namespace.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 9451b12a9b6c..1e34de2fbd60 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -812,14 +812,16 @@ static bool new_idmap_permitted(const struct file *file,
struct user_namespace *ns, int cap_setid,
struct uid_gid_map *new_map)
{
+ const struct cred *cred = file->f_cred;
/* Don't allow mappings that would allow anything that wouldn't
* be allowed without the establishment of unprivileged mappings.
*/
- if ((new_map->nr_extents == 1) && (new_map->extent[0].count == 1)) {
+ if ((new_map->nr_extents == 1) && (new_map->extent[0].count == 1) &&
+ uid_eq(ns->owner, cred->euid)) {
u32 id = new_map->extent[0].lower_first;
if (cap_setid == CAP_SETUID) {
kuid_t uid = make_kuid(ns->parent, id);
- if (uid_eq(uid, file->f_cred->euid))
+ if (uid_eq(uid, cred->euid))
return true;
}
}
--
2.1.0

80
userns-Rename-id_map_mutex-to-userns_state_mutex.patch Normal file
View File

@ -0,0 +1,80 @@
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Tue, 9 Dec 2014 14:03:14 -0600
Subject: [PATCH] userns: Rename id_map_mutex to userns_state_mutex
Generalize id_map_mutex so it can be used for more state of a user namespace.
Cc: stable@vger.kernel.org
Reviewed-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
kernel/user_namespace.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 1e34de2fbd60..44a555ac6104 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -24,6 +24,7 @@
#include <linux/fs_struct.h>
static struct kmem_cache *user_ns_cachep __read_mostly;
+static DEFINE_MUTEX(userns_state_mutex);
static bool new_idmap_permitted(const struct file *file,
struct user_namespace *ns, int cap_setid,
@@ -583,9 +584,6 @@ static bool mappings_overlap(struct uid_gid_map *new_map,
return false;
}
-
-static DEFINE_MUTEX(id_map_mutex);
-
static ssize_t map_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos,
int cap_setid,
@@ -602,7 +600,7 @@ static ssize_t map_write(struct file *file, const char __user *buf,
ssize_t ret = -EINVAL;
/*
- * The id_map_mutex serializes all writes to any given map.
+ * The userns_state_mutex serializes all writes to any given map.
*
* Any map is only ever written once.
*
@@ -620,7 +618,7 @@ static ssize_t map_write(struct file *file, const char __user *buf,
* order and smp_rmb() is guaranteed that we don't have crazy
* architectures returning stale data.
*/
- mutex_lock(&id_map_mutex);
+ mutex_lock(&userns_state_mutex);
ret = -EPERM;
/* Only allow one successful write to the map */
@@ -750,7 +748,7 @@ static ssize_t map_write(struct file *file, const char __user *buf,
*ppos = count;
ret = count;
out:
- mutex_unlock(&id_map_mutex);
+ mutex_unlock(&userns_state_mutex);
if (page)
free_page(page);
return ret;
@@ -845,12 +843,12 @@ bool userns_may_setgroups(const struct user_namespace *ns)
{
bool allowed;
- mutex_lock(&id_map_mutex);
+ mutex_lock(&userns_state_mutex);
/* It is not safe to use setgroups until a gid mapping in
* the user namespace has been established.
*/
allowed = ns->gid_map.nr_extents != 0;
- mutex_unlock(&id_map_mutex);
+ mutex_unlock(&userns_state_mutex);
return allowed;
}
--
2.1.0

91
userns-Unbreak-the-unprivileged-remount-tests.patch Normal file
View File

@ -0,0 +1,91 @@
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Tue, 2 Dec 2014 13:56:30 -0600
Subject: [PATCH] userns: Unbreak the unprivileged remount tests
A security fix in caused the way the unprivileged remount tests were
using user namespaces to break. Tweak the way user namespaces are
being used so the test works again.
Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
.../selftests/mount/unprivileged-remount-test.c | 32 ++++++++++++++++------
1 file changed, 24 insertions(+), 8 deletions(-)
diff --git a/tools/testing/selftests/mount/unprivileged-remount-test.c b/tools/testing/selftests/mount/unprivileged-remount-test.c
index 9669d375625a..517785052f1c 100644
--- a/tools/testing/selftests/mount/unprivileged-remount-test.c
+++ b/tools/testing/selftests/mount/unprivileged-remount-test.c
@@ -53,17 +53,14 @@ static void die(char *fmt, ...)
exit(EXIT_FAILURE);
}
-static void write_file(char *filename, char *fmt, ...)
+static void vmaybe_write_file(bool enoent_ok, char *filename, char *fmt, va_list ap)
{
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));
@@ -74,6 +71,8 @@ static void write_file(char *filename, char *fmt, ...)
fd = open(filename, O_WRONLY);
if (fd < 0) {
+ if ((errno == ENOENT) && enoent_ok)
+ return;
die("open of %s failed: %s\n",
filename, strerror(errno));
}
@@ -92,6 +91,26 @@ static void write_file(char *filename, char *fmt, ...)
}
}
+static void maybe_write_file(char *filename, char *fmt, ...)
+{
+ va_list ap;
+
+ va_start(ap, fmt);
+ vmaybe_write_file(true, filename, fmt, ap);
+ va_end(ap);
+
+}
+
+static void write_file(char *filename, char *fmt, ...)
+{
+ va_list ap;
+
+ va_start(ap, fmt);
+ vmaybe_write_file(false, filename, fmt, ap);
+ va_end(ap);
+
+}
+
static int read_mnt_flags(const char *path)
{
int ret;
@@ -144,13 +163,10 @@ static void create_and_enter_userns(void)
strerror(errno));
}
+ maybe_write_file("/proc/self/setgroups", "deny");
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));
--
2.1.0