Commit 6814ef2d authored by Alexey Gladkov's avatar Alexey Gladkov Committed by Eric W. Biederman
Browse files

proc: add option to mount only a pids subset 



This allows to hide all files and directories in the procfs that are not
related to tasks.

Signed-off-by: default avatarAlexey Gladkov <gladkov.alexey@gmail.com>
Reviewed-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
parent 24a71ce5

fs/proc/generic.c

+9 −0
Original line number Diff line number Diff line
@@ -269,6 +269,11 @@ struct dentry *proc_lookup_de(struct inode *dir, struct dentry *dentry, 
struct dentry *proc_lookup(struct inode *dir, struct dentry *dentry,

		unsigned int flags)

{

	struct proc_fs_info *fs_info = proc_sb_info(dir->i_sb);



	if (fs_info->pidonly == PROC_PIDONLY_ON)

		return ERR_PTR(-ENOENT);



	return proc_lookup_de(dir, dentry, PDE(dir));

}
@@ -325,6 +330,10 @@ int proc_readdir_de(struct file *file, struct dir_context *ctx, 
int proc_readdir(struct file *file, struct dir_context *ctx)

{

	struct inode *inode = file_inode(file);

	struct proc_fs_info *fs_info = proc_sb_info(inode->i_sb);



	if (fs_info->pidonly == PROC_PIDONLY_ON)

		return 1;



	return proc_readdir_de(file, ctx, PDE(inode));

}

fs/proc/inode.c

+6 −0
Original line number Diff line number Diff line
@@ -173,6 +173,8 @@ static int proc_show_options(struct seq_file *seq, struct dentry *root) 
		seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, fs_info->pid_gid));

	if (fs_info->hide_pid != HIDEPID_OFF)

		seq_printf(seq, ",hidepid=%u", fs_info->hide_pid);

	if (fs_info->pidonly != PROC_PIDONLY_OFF)

		seq_printf(seq, ",subset=pid");



	return 0;

}
@@ -463,6 +465,7 @@ proc_reg_get_unmapped_area(struct file *file, unsigned long orig_addr, 


static int proc_reg_open(struct inode *inode, struct file *file)

{

	struct proc_fs_info *fs_info = proc_sb_info(inode->i_sb);

	struct proc_dir_entry *pde = PDE(inode);

	int rv = 0;

	typeof_member(struct proc_ops, proc_open) open;
@@ -476,6 +479,9 @@ static int proc_reg_open(struct inode *inode, struct file *file) 
		return rv;

	}



	if (fs_info->pidonly == PROC_PIDONLY_ON)

		return -ENOENT;



	/*

	 * Ensure that

	 * 1) PDE's ->release hook will be called no matter what

fs/proc/root.c

+33 −0
Original line number Diff line number Diff line
@@ -34,16 +34,19 @@ struct proc_fs_context { 
	unsigned int		mask;

	int			hidepid;

	int			gid;

	int			pidonly;

};



enum proc_param {

	Opt_gid,

	Opt_hidepid,

	Opt_subset,

};



static const struct fs_parameter_spec proc_fs_parameters[] = {

	fsparam_u32("gid",	Opt_gid),

	fsparam_u32("hidepid",	Opt_hidepid),

	fsparam_string("subset",	Opt_subset),

	{}

};
@@ -55,6 +58,29 @@ static inline int valid_hidepid(unsigned int value) 
		value == HIDEPID_NOT_PTRACEABLE);

}



static int proc_parse_subset_param(struct fs_context *fc, char *value)

{

	struct proc_fs_context *ctx = fc->fs_private;



	while (value) {

		char *ptr = strchr(value, ',');



		if (ptr != NULL)

			*ptr++ = '\0';



		if (*value != '\0') {

			if (!strcmp(value, "pid")) {

				ctx->pidonly = PROC_PIDONLY_ON;

			} else {

				return invalf(fc, "proc: unsupported subset option - %s\n", value);

			}

		}

		value = ptr;

	}



	return 0;

}



static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param)

{

	struct proc_fs_context *ctx = fc->fs_private;
@@ -76,6 +102,11 @@ static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param) 
		ctx->hidepid = result.uint_32;

		break;



	case Opt_subset:

		if (proc_parse_subset_param(fc, param->string) < 0)

			return -EINVAL;

		break;



	default:

		return -EINVAL;

	}
@@ -94,6 +125,8 @@ static void proc_apply_options(struct proc_fs_info *fs_info, 
		fs_info->pid_gid = make_kgid(user_ns, ctx->gid);

	if (ctx->mask & (1 << Opt_hidepid))

		fs_info->hide_pid = ctx->hidepid;

	if (ctx->mask & (1 << Opt_subset))

		fs_info->pidonly = ctx->pidonly;

}



static int proc_fill_super(struct super_block *s, struct fs_context *fc)

include/linux/proc_fs.h

+7 −0
Original line number Diff line number Diff line
@@ -50,12 +50,19 @@ enum { 
	HIDEPID_NOT_PTRACEABLE = 4, /* Limit pids to only ptraceable pids */

};



/* definitions for proc mount option pidonly */

enum {

	PROC_PIDONLY_OFF = 0,

	PROC_PIDONLY_ON  = 1,

};



struct proc_fs_info {

	struct pid_namespace *pid_ns;

	struct dentry *proc_self;        /* For /proc/self */

	struct dentry *proc_thread_self; /* For /proc/thread-self */

	kgid_t pid_gid;

	int hide_pid;

	int pidonly;

};



static inline struct proc_fs_info *proc_sb_info(struct super_block *sb)