procfs: parse mount options

index 7737c54..9b9f92a 100644
@@ -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 @@ void __init proc_init_inodecache(void)
 					     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)

index 7838e5c..2925775 100644
@@ -117,6 +117,7 @@ void pde_put(struct proc_dir_entry *pde);
 
 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

82 lines not on this page · raw message

index 2db1bd3..8caf5cb 100644
@@ -627,6 +627,45 @@ int proc_setattr(struct dentry *dentry, struct iattr *attr)
 	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 = get_proc_task(inode);
+
+	if (!has_pid_permissions(pid, task, 1)) {
+		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,
 };

@@ -1757,6 +1796,7 @@ int pid_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
 	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);
 

@@ -1765,6 +1805,14 @@ int pid_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
 	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);

@@ -2935,6 +2983,7 @@ static const struct inode_operations proc_tgid_base_inode_operations = {
 	.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)

@@ -3138,6 +3187,12 @@ static int proc_pid_fill_cache(struct file *filp, void *dirent, filldir_t filldi
 				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)
 {

@@ -3145,6 +3200,7 @@ int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir)
 	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;

@@ -3166,8 +3222,13 @@ int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir)
 	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;
 		}

@@ -3502,6 +3563,7 @@ static const struct inode_operations proc_task_inode_operations = {
 	.lookup		= proc_task_lookup,
 	.getattr	= proc_task_getattr,
 	.setattr	= proc_setattr,
+	.permission	= proc_pid_permission,
 };
 
 static const struct file_operations proc_task_operations = {

index 9b9f92a..6b5d927 100644
@@ -107,6 +107,14 @@ void __init proc_init_inodecache(void)
 
 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;
 }
 

index 165a0d1..73af7b2 100644
@@ -38,10 +38,12 @@ static int proc_set_super(struct super_block *sb, void *data)
 }
 
 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},
 };
 

@@ -49,6 +51,7 @@ static int proc_parse_options(char *options, struct pid_namespace *pid)
 {
 	char *p;
 	substring_t args[MAX_OPT_ARGS];
+	int option;
 
 	pr_debug("proc: options = %s\n", options);
 

@@ -63,6 +66,20 @@ static int proc_parse_options(char *options, struct pid_namespace *pid)
 		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);

index 38d1032..e7cf666 100644
@@ -30,6 +30,8 @@ struct pid_namespace {
 #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;