[PATCH 18/38] proc: Add fs_context support to procfs [ver #10]

David Howells
2018-07-27T17:33:30Z

Add fs_context support to procfs.

Signed-off-by: David Howells <dhowells@redhat.com>
---

fs/proc/inode.c | 2
fs/proc/internal.h | 2
fs/proc/root.c | 209 +++++++++++++++++++++++++++++++++++-----------------
3 files changed, 141 insertions(+), 72 deletions(-)

diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index c5e7bbf81e10..38155bec4a54 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -127,7 +127,7 @@ const struct super_operations proc_sops = {
.drop_inode = generic_delete_inode,
.evict_inode = proc_evict_inode,
.statfs = simple_statfs,
- .remount_fs = proc_remount,
+ .reconfigure = proc_reconfigure,
.show_options = proc_show_options,
};

diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index bfe2bea2c71d..ea8c5468eafc 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -273,7 +273,7 @@ static inline void proc_tty_init(void) {}
extern struct proc_dir_entry proc_root;

extern void proc_self_init(void);
-extern int proc_remount(struct super_block *, int *, char *, size_t);
+extern int proc_reconfigure(struct super_block *, struct fs_context *);

/*
* task_[no]mmu.c
diff --git a/fs/proc/root.c b/fs/proc/root.c
index 15da85cefd3f..662ce77eaeb7 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -19,74 +19,98 @@
#include <linux/module.h>
#include <linux/bitops.h>
#include <linux/user_namespace.h>
+#include <linux/fs_context.h>
#include <linux/mount.h>
#include <linux/pid_namespace.h>
-#include <linux/parser.h>
+#include <linux/fs_parser.h>
#include <linux/cred.h>
#include <linux/magic.h>
+#include <linux/slab.h>

#include "internal.h"

-enum {
- Opt_gid, Opt_hidepid, Opt_err,
+struct proc_fs_context {
+ struct pid_namespace *pid_ns;
+ unsigned long mask;
+ int hidepid;
+ int gid;
};

-static const match_table_t tokens = {
- {Opt_hidepid, "hidepid=%u"},
- {Opt_gid, "gid=%u"},
- {Opt_err, NULL},
+enum proc_param {
+ Opt_gid,
+ Opt_hidepid,
+ nr__proc_params
};

-static int proc_parse_options(char *options, struct pid_namespace *pid)
+static const struct fs_parameter_spec proc_param_specs[nr__proc_params] = {
+ [Opt_gid] = { fs_param_is_u32 },
+ [Opt_hidepid] = { fs_param_is_u32 },
+};
+
+static const struct constant_table proc_param_keys[] = {
+ { "gid", Opt_gid },
+ { "hidepid", Opt_hidepid },
+};
+
+static const struct fs_parameter_description proc_fs_parameters = {
+ .name = "proc",
+ .nr_params = nr__proc_params,
+ .nr_keys = ARRAY_SIZE(proc_param_keys),
+ .keys = proc_param_keys,
+ .specs = proc_param_specs,
+ .no_source = true,
+};
+
+static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param)
{
- char *p;
- substring_t args[MAX_OPT_ARGS];
- int option;
-
- if (!options)
- return 1;
-
- while ((p = strsep(&options, ",")) != NULL) {
- int token;
- if (!*p)
- continue;
-
- args[0].to = args[0].from = NULL;
- token = match_token(p, tokens, args);
- switch (token) {
- case Opt_gid:
- if (match_int(&args[0], &option))
- return 0;
- pid->pid_gid = make_kgid(current_user_ns(), option);
- break;
- case Opt_hidepid:
- if (match_int(&args[0], &option))
- return 0;
- if (option < HIDEPID_OFF ||
- option > HIDEPID_INVISIBLE) {
- 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);
- return 0;
- }
+ struct proc_fs_context *ctx = fc->fs_private;
+ struct fs_parse_result result;
+ int ret;
+
+ ret = fs_parse(fc, &proc_fs_parameters, param, &result);
+ if (ret <= 0)
+ return ret;
+
+ switch (result.key) {
+ case Opt_gid:
+ ctx->gid = result.uint_32;
+ break;
+
+ case Opt_hidepid:
+ ctx->hidepid = result.uint_32;
+ if (ctx->hidepid < HIDEPID_OFF ||
+ ctx->hidepid > HIDEPID_INVISIBLE)
+ return invalf(fc, "proc: hidepid value must be between 0 and 2.\n");
+ break;
+
+ default:
+ return -EINVAL;
}

- return 1;
+ ctx->mask |= 1 << result.key;
+ return 0;
+}
+
+static void proc_apply_options(struct super_block *s,
+ struct fs_context *fc,
+ struct pid_namespace *pid_ns,
+ struct user_namespace *user_ns)
+{
+ struct proc_fs_context *ctx = fc->fs_private;
+
+ if (ctx->mask & (1 << Opt_gid))
+ pid_ns->pid_gid = make_kgid(user_ns, ctx->gid);
+ if (ctx->mask & (1 << Opt_hidepid))
+ pid_ns->hide_pid = ctx->hidepid;
}

-static int proc_fill_super(struct super_block *s, void *data, size_t data_size, int silent)
+static int proc_fill_super(struct super_block *s, struct fs_context *fc)
{
- struct pid_namespace *ns = get_pid_ns(s->s_fs_info);
+ struct pid_namespace *pid_ns = get_pid_ns(s->s_fs_info);
struct inode *root_inode;
int ret;

- if (!proc_parse_options(data, ns))
- return -EINVAL;
+ proc_apply_options(s, fc, pid_ns, current_user_ns());

/* User space would break if executables or devices appear on proc */
s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV;
@@ -103,7 +127,7 @@ static int proc_fill_super(struct super_block *s, void *data, size_t data_size,
* top of it
*/
s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH;
-
+
pde_get(&proc_root);
root_inode = proc_get_inode(s, &proc_root);
if (!root_inode) {
@@ -124,30 +148,52 @@ static int proc_fill_super(struct super_block *s, void *data, size_t data_size,
return proc_setup_thread_self(s);
}

-int proc_remount(struct super_block *sb, int *flags,
- char *data, size_t data_size)
+int proc_reconfigure(struct super_block *sb, struct fs_context *fc)
{
struct pid_namespace *pid = sb->s_fs_info;

sync_filesystem(sb);
- return !proc_parse_options(data, pid);
+
+ if (fc)
+ proc_apply_options(sb, fc, pid, current_user_ns());
+ return 0;
}

-static struct dentry *proc_mount(struct file_system_type *fs_type,
- int flags, const char *dev_name,
- void *data, size_t data_size)
+static int proc_get_tree(struct fs_context *fc)
{
- struct pid_namespace *ns;
+ struct proc_fs_context *ctx = fc->fs_private;

- if (flags & SB_KERNMOUNT) {
- ns = data;
- data = NULL;
- } else {
- ns = task_active_pid_ns(current);
- }
+ fc->s_fs_info = ctx->pid_ns;
+ return vfs_get_super(fc, vfs_get_keyed_super, proc_fill_super);
+}
+
+static void proc_fs_context_free(struct fs_context *fc)
+{
+ struct proc_fs_context *ctx = fc->fs_private;
+
+ if (ctx->pid_ns)
+ put_pid_ns(ctx->pid_ns);
+ kfree(ctx);
+}
+
+static const struct fs_context_operations proc_fs_context_ops = {
+ .free = proc_fs_context_free,
+ .parse_param = proc_parse_param,
+ .get_tree = proc_get_tree,
+};

- return mount_ns(fs_type, flags, data, data_size, ns, ns->user_ns,
- proc_fill_super);
+static int proc_init_fs_context(struct fs_context *fc, struct dentry *reference)
+{
+ struct proc_fs_context *ctx;
+
+ ctx = kzalloc(sizeof(struct proc_fs_context), GFP_KERNEL);
+ if (!ctx)
+ return -ENOMEM;
+
+ ctx->pid_ns = get_pid_ns(task_active_pid_ns(current));
+ fc->fs_private = ctx;
+ fc->ops = &proc_fs_context_ops;
+ return 0;
}

static void proc_kill_sb(struct super_block *sb)
@@ -164,10 +210,11 @@ static void proc_kill_sb(struct super_block *sb)
}

static struct file_system_type proc_fs_type = {
- .name = "proc",
- .mount = proc_mount,
- .kill_sb = proc_kill_sb,
- .fs_flags = FS_USERNS_MOUNT,
+ .name = "proc",
+ .init_fs_context = proc_init_fs_context,
+ .parameters = &proc_fs_parameters,
+ .kill_sb = proc_kill_sb,
+ .fs_flags = FS_USERNS_MOUNT,
};

void __init proc_root_init(void)
@@ -205,7 +252,7 @@ static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentr
{
if (!proc_pid_lookup(dir, dentry, flags))
return NULL;
-
+
return proc_lookup(dir, dentry, flags);
}

@@ -258,9 +305,31 @@ struct proc_dir_entry proc_root = {

int pid_ns_prepare_proc(struct pid_namespace *ns)
{
+ struct proc_fs_context *ctx;
+ struct fs_context *fc;
struct vfsmount *mnt;
+ int ret;
+
+ fc = vfs_new_fs_context(&proc_fs_type, NULL, 0,
+ FS_CONTEXT_FOR_KERNEL_MOUNT);
+ if (IS_ERR(fc))
+ return PTR_ERR(fc);
+
+ ctx = fc->fs_private;
+ if (ctx->pid_ns != ns) {
+ put_pid_ns(ctx->pid_ns);
+ get_pid_ns(ns);
+ ctx->pid_ns = ns;
+ }
+
+ ret = vfs_get_tree(fc);
+ if (ret < 0) {
+ put_fs_context(fc);
+ return ret;
+ }

- mnt = kern_mount_data(&proc_fs_type, ns, 0);
+ mnt = vfs_create_mount(fc, 0);
+ put_fs_context(fc);
if (IS_ERR(mnt))
return PTR_ERR(mnt);