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Subject[PATCH v5 2/7] proc: move /proc/{self|thread-self} dentries to proc_fs_info
From: Djalal Harouni <tixxdz@gmail.com>

This is a preparation patch that moves /proc/{self|thread-self} dentries
to be stored inside procfs fs_info struct instead of making them per pid
namespace. Since we want to support multiple procfs instances we need to
make sure that these dentries are also per-superblock instead of
per-pidns, unmounting a private procfs won't clash with other procfs
mounts.

Cc: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Djalal Harouni <tixxdz@gmail.com>
---
fs/proc/base.c | 4 ++--
fs/proc/root.c | 8 ++++----
fs/proc/self.c | 3 +--
fs/proc/thread_self.c | 5 ++---
include/linux/pid_namespace.h | 4 +---
include/linux/proc_fs.h | 2 ++
6 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 99a0f24..e0c2afc 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -3252,13 +3252,13 @@ int proc_pid_readdir(struct file *file, struct dir_context *ctx)
return 0;

if (pos == TGID_OFFSET - 2) {
- struct inode *inode = d_inode(ns->proc_self);
+ struct inode *inode = d_inode(fs_info->proc_self);
if (!dir_emit(ctx, "self", 4, inode->i_ino, DT_LNK))
return 0;
ctx->pos = pos = pos + 1;
}
if (pos == TGID_OFFSET - 1) {
- struct inode *inode = d_inode(ns->proc_thread_self);
+ struct inode *inode = d_inode(fs_info->proc_thread_self);
if (!dir_emit(ctx, "thread-self", 11, inode->i_ino, DT_LNK))
return 0;
ctx->pos = pos = pos + 1;
diff --git a/fs/proc/root.c b/fs/proc/root.c
index 5d4c454..184c42b 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -162,10 +162,10 @@ static void proc_kill_sb(struct super_block *sb)
struct proc_fs_info *fs_info = proc_sb(sb);
struct pid_namespace *ns = (struct pid_namespace *)fs_info->pid_ns;

- if (ns->proc_self)
- dput(ns->proc_self);
- if (ns->proc_thread_self)
- dput(ns->proc_thread_self);
+ if (fs_info->proc_self)
+ dput(fs_info->proc_self);
+ if (fs_info->proc_thread_self)
+ dput(fs_info->proc_thread_self);
kill_anon_super(sb);
put_pid_ns(ns);
kfree(fs_info);
diff --git a/fs/proc/self.c b/fs/proc/self.c
index 3f2a88f..9ad3c55 100644
--- a/fs/proc/self.c
+++ b/fs/proc/self.c
@@ -38,7 +38,6 @@ int proc_setup_self(struct super_block *s)
{
struct inode *root_inode = d_inode(s->s_root);
struct proc_fs_info *fs_info = proc_sb(s);
- struct pid_namespace *ns = fs_info->pid_ns;
struct dentry *self;

inode_lock(root_inode);
@@ -65,7 +64,7 @@ int proc_setup_self(struct super_block *s)
pr_err("proc_fill_super: can't allocate /proc/self\n");
return PTR_ERR(self);
}
- ns->proc_self = self;
+ fs_info->proc_self = self;
return 0;
}

diff --git a/fs/proc/thread_self.c b/fs/proc/thread_self.c
index e80dd79..8db3503 100644
--- a/fs/proc/thread_self.c
+++ b/fs/proc/thread_self.c
@@ -37,7 +37,6 @@ static unsigned thread_self_inum __ro_after_init;
int proc_setup_thread_self(struct super_block *s)
{
struct proc_fs_info *fs_info = proc_sb(s);
- struct pid_namespace *ns = fs_info->pid_ns;
struct inode *root_inode = d_inode(s->s_root);
struct dentry *thread_self;

@@ -62,10 +61,10 @@ int proc_setup_thread_self(struct super_block *s)
}
inode_unlock(root_inode);
if (IS_ERR(thread_self)) {
- pr_err("proc_fill_super: can't allocate /proc/thread_self\n");
+ pr_err("proc_fill_super: can't allocate /proc/thread-self\n");
return PTR_ERR(thread_self);
}
- ns->proc_thread_self = thread_self;
+ fs_info->proc_thread_self = thread_self;
return 0;
}

diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index 49538b1..f91a8bf 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -31,9 +31,7 @@ struct pid_namespace {
unsigned int level;
struct pid_namespace *parent;
#ifdef CONFIG_PROC_FS
- struct vfsmount *proc_mnt;
- struct dentry *proc_self;
- struct dentry *proc_thread_self;
+ struct vfsmount *proc_mnt; /* Internal proc mounted during each new pidns */
#endif
#ifdef CONFIG_BSD_PROCESS_ACCT
struct fs_pin *bacct;
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index 7c8cf3c..5e461f6 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -11,6 +11,8 @@

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/ */
};

struct proc_dir_entry;
--
2.10.5
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