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proc: Backport hidepid mount option from Linux 3.4 (Closes: #669028) 

svn path=/dists/sid/linux/; revision=19095
This commit is contained in:
Ben Hutchings 2012-06-07 06:59:12 +00:00
parent dbf716c798
commit de6102258b
6 changed files with 597 additions and 0 deletions
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1
debian/changelog vendored
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@ -21,6 +21,7 @@ linux (3.2.19-2) UNRELEASED; urgency=low
modules as required even if they are built-in in some configurations
* filter: Allow to create sk-unattached filters
* net: Backport team driver from Linux 3.5-rc1
* proc: Backport hidepid mount option from Linux 3.4 (Closes: #669028)
-- Ben Hutchings <ben@decadent.org.uk> Sat, 02 Jun 2012 20:31:53 +0100

167
debian/patches/features/all/hidepid/0001-procfs-parse-mount-options.patch vendored Normal file
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@ -0,0 +1,167 @@
From: Vasiliy Kulikov <segooon@gmail.com>
Date: Tue, 10 Jan 2012 15:11:27 -0800
Subject: procfs: parse mount options
commit 97412950b10e64f347aec4a9b759395c2465adf6 upstream.
Add support for procfs mount options. Actual mount options are coming in
the next patches.
Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Greg KH <greg@kroah.com>
Cc: Theodore Tso <tytso@MIT.EDU>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: James Morris <jmorris@namei.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 3.2: super_operations::show_options takes a
struct vfsmount *, not struct dentry *]
---
fs/proc/inode.c | 10 ++++++++++
fs/proc/internal.h | 1 +
fs/proc/root.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++--
3 files changed, 64 insertions(+), 2 deletions(-)
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -7,6 +7,7 @@
#include <linux/time.h>
#include <linux/proc_fs.h>
#include <linux/kernel.h>
+#include <linux/pid_namespace.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/stat.h>
@@ -17,7 +18,9 @@
#include <linux/init.h>
#include <linux/module.h>
#include <linux/sysctl.h>
+#include <linux/seq_file.h>
#include <linux/slab.h>
+#include <linux/mount.h>
#include <asm/system.h>
#include <asm/uaccess.h>
@@ -102,12 +105,19 @@
init_once);
}
+static int proc_show_options(struct seq_file *seq, struct vfsmount *vfs)
+{
+ return 0;
+}
+
static const struct super_operations proc_sops = {
.alloc_inode = proc_alloc_inode,
.destroy_inode = proc_destroy_inode,
.drop_inode = generic_delete_inode,
.evict_inode = proc_evict_inode,
.statfs = simple_statfs,
+ .remount_fs = proc_remount,
+ .show_options = proc_show_options,
};
static void __pde_users_dec(struct proc_dir_entry *pde)
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -117,6 +117,7 @@
int proc_fill_super(struct super_block *);
struct inode *proc_get_inode(struct super_block *, struct proc_dir_entry *);
+int proc_remount(struct super_block *sb, int *flags, char *data);
/*
* These are generic /proc routines that use the internal
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -18,6 +18,7 @@
#include <linux/bitops.h>
#include <linux/mount.h>
#include <linux/pid_namespace.h>
+#include <linux/parser.h>
#include "internal.h"
@@ -36,6 +37,48 @@
return err;
}
+enum {
+ Opt_err,
+};
+
+static const match_table_t tokens = {
+ {Opt_err, NULL},
+};
+
+static int proc_parse_options(char *options, struct pid_namespace *pid)
+{
+ char *p;
+ substring_t args[MAX_OPT_ARGS];
+
+ pr_debug("proc: options = %s\n", options);
+
+ if (!options)
+ return 1;
+
+ while ((p = strsep(&options, ",")) != NULL) {
+ int token;
+ if (!*p)
+ continue;
+
+ args[0].to = args[0].from = 0;
+ token = match_token(p, tokens, args);
+ switch (token) {
+ default:
+ pr_err("proc: unrecognized mount option \"%s\" "
+ "or missing value\n", p);
+ return 0;
+ }
+ }
+
+ return 1;
+}
+
+int proc_remount(struct super_block *sb, int *flags, char *data)
+{
+ struct pid_namespace *pid = sb->s_fs_info;
+ return !proc_parse_options(data, pid);
+}
+
static struct dentry *proc_mount(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data)
{
@@ -43,11 +86,15 @@
struct super_block *sb;
struct pid_namespace *ns;
struct proc_inode *ei;
+ char *options;
- if (flags & MS_KERNMOUNT)
+ if (flags & MS_KERNMOUNT) {
ns = (struct pid_namespace *)data;
- else
+ options = NULL;
+ } else {
ns = current->nsproxy->pid_ns;
+ options = data;
+ }
sb = sget(fs_type, proc_test_super, proc_set_super, ns);
if (IS_ERR(sb))
@@ -55,6 +102,10 @@
if (!sb->s_root) {
sb->s_flags = flags;
+ if (!proc_parse_options(options, ns)) {
+ deactivate_locked_super(sb);
+ return ERR_PTR(-EINVAL);
+ }
err = proc_fill_super(sb);
if (err) {
deactivate_locked_super(sb);

332
debian/patches/features/all/hidepid/0002-procfs-add-hidepid-and-gid-mount-options.patch vendored Normal file
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@ -0,0 +1,332 @@
From: Vasiliy Kulikov <segooon@gmail.com>
Date: Tue, 10 Jan 2012 15:11:31 -0800
Subject: procfs: add hidepid= and gid= mount options
commit 0499680a42141d86417a8fbaa8c8db806bea1201 upstream.
Add support for mount options to restrict access to /proc/PID/
directories. The default backward-compatible "relaxed" behaviour is left
untouched.
The first mount option is called "hidepid" and its value defines how much
info about processes we want to be available for non-owners:
hidepid=0 (default) means the old behavior - anybody may read all
world-readable /proc/PID/* files.
hidepid=1 means users may not access any /proc/<pid>/ directories, but
their own. Sensitive files like cmdline, sched*, status are now protected
against other users. As permission checking done in proc_pid_permission()
and files' permissions are left untouched, programs expecting specific
files' modes are not confused.
hidepid=2 means hidepid=1 plus all /proc/PID/ will be invisible to other
users. It doesn't mean that it hides whether a process exists (it can be
learned by other means, e.g. by kill -0 $PID), but it hides process' euid
and egid. It compicates intruder's task of gathering info about running
processes, whether some daemon runs with elevated privileges, whether
another user runs some sensitive program, whether other users run any
program at all, etc.
gid=XXX defines a group that will be able to gather all processes' info
(as in hidepid=0 mode). This group should be used instead of putting
nonroot user in sudoers file or something. However, untrusted users (like
daemons, etc.) which are not supposed to monitor the tasks in the whole
system should not be added to the group.
hidepid=1 or higher is designed to restrict access to procfs files, which
might reveal some sensitive private information like precise keystrokes
timings:
http://www.openwall.com/lists/oss-security/2011/11/05/3
hidepid=1/2 doesn't break monitoring userspace tools. ps, top, pgrep, and
conky gracefully handle EPERM/ENOENT and behave as if the current user is
the only user running processes. pstree shows the process subtree which
contains "pstree" process.
Note: the patch doesn't deal with setuid/setgid issues of keeping
preopened descriptors of procfs files (like
https://lkml.org/lkml/2011/2/7/368). We rely on that the leaked
information like the scheduling counters of setuid apps doesn't threaten
anybody's privacy - only the user started the setuid program may read the
counters.
Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Greg KH <greg@kroah.com>
Cc: Theodore Tso <tytso@MIT.EDU>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: James Morris <jmorris@namei.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 3.2: super_operations::show_options takes a
struct vfsmount *, not struct dentry *]
---
Documentation/filesystems/proc.txt | 39 ++++++++++++++++++++
fs/proc/base.c | 69 +++++++++++++++++++++++++++++++++++-
fs/proc/inode.c | 8 +++++
fs/proc/root.c | 21 +++++++++--
include/linux/pid_namespace.h | 2 ++
5 files changed, 135 insertions(+), 4 deletions(-)
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -41,6 +41,8 @@
3.5 /proc/<pid>/mountinfo - Information about mounts
3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
+ 4 Configuring procfs
+ 4.1 Mount options
------------------------------------------------------------------------------
Preface
@@ -1542,3 +1544,40 @@
is limited in size compared to the cmdline value, so writing anything longer
then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
comm value.
+
+
+------------------------------------------------------------------------------
+Configuring procfs
+------------------------------------------------------------------------------
+
+4.1 Mount options
+---------------------
+
+The following mount options are supported:
+
+ hidepid= Set /proc/<pid>/ access mode.
+ gid= Set the group authorized to learn processes information.
+
+hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories
+(default).
+
+hidepid=1 means users may not access any /proc/<pid>/ directories but their
+own. Sensitive files like cmdline, sched*, status are now protected against
+other users. This makes it impossible to learn whether any user runs
+specific program (given the program doesn't reveal itself by its behaviour).
+As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users,
+poorly written programs passing sensitive information via program arguments are
+now protected against local eavesdroppers.
+
+hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other
+users. It doesn't mean that it hides a fact whether a process with a specific
+pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"),
+but it hides process' uid and gid, which may be learned by stat()'ing
+/proc/<pid>/ otherwise. It greatly complicates an intruder's task of gathering
+information about running processes, whether some daemon runs with elevated
+privileges, whether other user runs some sensitive program, whether other users
+run any program at all, etc.
+
+gid= defines a group authorized to learn processes information otherwise
+prohibited by hidepid=. If you use some daemon like identd which needs to learn
+information about processes information, just add identd to this group.
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -574,6 +574,50 @@
return 0;
}
+/*
+ * May current process learn task's sched/cmdline info (for hide_pid_min=1)
+ * or euid/egid (for hide_pid_min=2)?
+ */
+static bool has_pid_permissions(struct pid_namespace *pid,
+ struct task_struct *task,
+ int hide_pid_min)
+{
+ if (pid->hide_pid < hide_pid_min)
+ return true;
+ if (in_group_p(pid->pid_gid))
+ return true;
+ return ptrace_may_access(task, PTRACE_MODE_READ);
+}
+
+
+static int proc_pid_permission(struct inode *inode, int mask)
+{
+ struct pid_namespace *pid = inode->i_sb->s_fs_info;
+ struct task_struct *task;
+ bool has_perms;
+
+ task = get_proc_task(inode);
+ has_perms = has_pid_permissions(pid, task, 1);
+ put_task_struct(task);
+
+ if (!has_perms) {
+ if (pid->hide_pid == 2) {
+ /*
+ * Let's make getdents(), stat(), and open()
+ * consistent with each other. If a process
+ * may not stat() a file, it shouldn't be seen
+ * in procfs at all.
+ */
+ return -ENOENT;
+ }
+
+ return -EPERM;
+ }
+ return generic_permission(inode, mask);
+}
+
+
+
static const struct inode_operations proc_def_inode_operations = {
.setattr = proc_setattr,
};
@@ -1642,6 +1686,7 @@
struct inode *inode = dentry->d_inode;
struct task_struct *task;
const struct cred *cred;
+ struct pid_namespace *pid = dentry->d_sb->s_fs_info;
generic_fillattr(inode, stat);
@@ -1650,6 +1695,14 @@
stat->gid = 0;
task = pid_task(proc_pid(inode), PIDTYPE_PID);
if (task) {
+ if (!has_pid_permissions(pid, task, 2)) {
+ rcu_read_unlock();
+ /*
+ * This doesn't prevent learning whether PID exists,
+ * it only makes getattr() consistent with readdir().
+ */
+ return -ENOENT;
+ }
if ((inode->i_mode == (S_IFDIR|S_IRUGO|S_IXUGO)) ||
task_dumpable(task)) {
cred = __task_cred(task);
@@ -2794,6 +2847,7 @@
.lookup = proc_tgid_base_lookup,
.getattr = pid_getattr,
.setattr = proc_setattr,
+ .permission = proc_pid_permission,
};
static void proc_flush_task_mnt(struct vfsmount *mnt, pid_t pid, pid_t tgid)
@@ -2997,6 +3051,12 @@
proc_pid_instantiate, iter.task, NULL);
}
+static int fake_filldir(void *buf, const char *name, int namelen,
+ loff_t offset, u64 ino, unsigned d_type)
+{
+ return 0;
+}
+
/* for the /proc/ directory itself, after non-process stuff has been done */
int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir)
{
@@ -3004,6 +3064,7 @@
struct task_struct *reaper;
struct tgid_iter iter;
struct pid_namespace *ns;
+ filldir_t __filldir;
if (filp->f_pos >= PID_MAX_LIMIT + TGID_OFFSET)
goto out_no_task;
@@ -3025,8 +3086,13 @@
for (iter = next_tgid(ns, iter);
iter.task;
iter.tgid += 1, iter = next_tgid(ns, iter)) {
+ if (has_pid_permissions(ns, iter.task, 2))
+ __filldir = filldir;
+ else
+ __filldir = fake_filldir;
+
filp->f_pos = iter.tgid + TGID_OFFSET;
- if (proc_pid_fill_cache(filp, dirent, filldir, iter) < 0) {
+ if (proc_pid_fill_cache(filp, dirent, __filldir, iter) < 0) {
put_task_struct(iter.task);
goto out;
}
@@ -3361,6 +3427,7 @@
.lookup = proc_task_lookup,
.getattr = proc_task_getattr,
.setattr = proc_setattr,
+ .permission = proc_pid_permission,
};
static const struct file_operations proc_task_operations = {
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -107,6 +107,14 @@
static int proc_show_options(struct seq_file *seq, struct vfsmount *vfs)
{
+ struct super_block *sb = vfs->mnt_sb;
+ struct pid_namespace *pid = sb->s_fs_info;
+
+ if (pid->pid_gid)
+ seq_printf(seq, ",gid=%lu", (unsigned long)pid->pid_gid);
+ if (pid->hide_pid != 0)
+ seq_printf(seq, ",hidepid=%u", pid->hide_pid);
+
return 0;
}
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -38,10 +38,12 @@
}
enum {
- Opt_err,
+ Opt_gid, Opt_hidepid, Opt_err,
};
static const match_table_t tokens = {
+ {Opt_hidepid, "hidepid=%u"},
+ {Opt_gid, "gid=%u"},
{Opt_err, NULL},
};
@@ -49,8 +51,7 @@
{
char *p;
substring_t args[MAX_OPT_ARGS];
-
- pr_debug("proc: options = %s\n", options);
+ int option;
if (!options)
return 1;
@@ -63,6 +64,20 @@
args[0].to = args[0].from = 0;
token = match_token(p, tokens, args);
switch (token) {
+ case Opt_gid:
+ if (match_int(&args[0], &option))
+ return 0;
+ pid->pid_gid = option;
+ break;
+ case Opt_hidepid:
+ if (match_int(&args[0], &option))
+ return 0;
+ if (option < 0 || option > 2) {
+ pr_err("proc: hidepid value must be between 0 and 2.\n");
+ return 0;
+ }
+ pid->hide_pid = option;
+ break;
default:
pr_err("proc: unrecognized mount option \"%s\" "
"or missing value\n", p);
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -30,6 +30,8 @@
#ifdef CONFIG_BSD_PROCESS_ACCT
struct bsd_acct_struct *bacct;
#endif
+ gid_t pid_gid;
+ int hide_pid;
};
extern struct pid_namespace init_pid_ns;

42
debian/patches/features/all/hidepid/0003-proc-fix-null-pointer-deref-in-proc_pid_permission.patch vendored Normal file
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@ -0,0 +1,42 @@
From: Xiaotian Feng <xtfeng@gmail.com>
Date: Thu, 12 Jan 2012 17:17:08 -0800
Subject: proc: fix null pointer deref in proc_pid_permission()
commit a2ef990ab5a6705a356d146dd773a3b359787497 upstream.
get_proc_task() can fail to search the task and return NULL,
put_task_struct() will then bomb the kernel with following oops:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
IP: [<ffffffff81217d34>] proc_pid_permission+0x64/0xe0
PGD 112075067 PUD 112814067 PMD 0
Oops: 0002 [#1] PREEMPT SMP
This is a regression introduced by commit 0499680a ("procfs: add hidepid=
and gid= mount options"). The kernel should return -ESRCH if
get_proc_task() failed.
Signed-off-by: Xiaotian Feng <dannyfeng@tencent.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Vasiliy Kulikov <segoon@openwall.com>
Cc: Stephen Wilson <wilsons@start.ca>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
fs/proc/base.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 8173dfd..5485a53 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -654,6 +654,8 @@ static int proc_pid_permission(struct inode *inode, int mask)
bool has_perms;
task = get_proc_task(inode);
+ if (!task)
+ return -ESRCH;
has_perms = has_pid_permissions(pid, task, 1);
put_task_struct(task);

49
debian/patches/features/all/hidepid/0004-proc-fix-mount-t-proc-o-AAA.patch vendored Normal file
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@ -0,0 +1,49 @@
From: Vasiliy Kulikov <segoon@openwall.com>
Date: Thu, 5 Apr 2012 14:25:04 -0700
Subject: proc: fix mount -t proc -o AAA
commit 99663be772c827b8f5f594fe87eb4807be1994e5 upstream.
The proc_parse_options() call from proc_mount() runs only once at boot
time. So on any later mount attempt, any mount options are ignored
because ->s_root is already initialized.
As a consequence, "mount -o <options>" will ignore the options. The
only way to change mount options is "mount -o remount,<options>".
To fix this, parse the mount options unconditionally.
Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
Reported-by: Arkadiusz Miskiewicz <a.miskiewicz@gmail.com>
Tested-by: Arkadiusz Miskiewicz <a.miskiewicz@gmail.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
fs/proc/root.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/fs/proc/root.c b/fs/proc/root.c
index 46a15d8..eed44bf 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -115,12 +115,13 @@ static struct dentry *proc_mount(struct file_system_type *fs_type,
if (IS_ERR(sb))
return ERR_CAST(sb);
+ if (!proc_parse_options(options, ns)) {
+ deactivate_locked_super(sb);
+ return ERR_PTR(-EINVAL);
+ }
+
if (!sb->s_root) {
sb->s_flags = flags;
- if (!proc_parse_options(options, ns)) {
- deactivate_locked_super(sb);
- return ERR_PTR(-EINVAL);
- }
err = proc_fill_super(sb);
if (err) {
deactivate_locked_super(sb);

6
debian/patches/series-all vendored
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@ -337,3 +337,9 @@ features/all/team/0020-team-add-missed-statics.patch
features/all/team/0021-team-lb-let-userspace-care-about-port-macs.patch
features/all/team/0022-team-allow-to-enable-disable-ports.patch
features/all/team/0023-team-add-per-port-option-for-enabling-disabling-port.patch
# procfs hidepid from 3.4
features/all/hidepid/0001-procfs-parse-mount-options.patch
features/all/hidepid/0002-procfs-add-hidepid-and-gid-mount-options.patch
features/all/hidepid/0003-proc-fix-null-pointer-deref-in-proc_pid_permission.patch
features/all/hidepid/0004-proc-fix-mount-t-proc-o-AAA.patch