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    Subject[PATCH v8 03/11] proc: move /proc/{self|thread-self} dentries to proc_fs_info
    Date
    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>
    Signed-off-by: Alexey Gladkov <gladkov.alexey@gmail.com>
    ---
    fs/proc/base.c | 5 +++--
    fs/proc/root.c | 8 ++++----
    fs/proc/self.c | 4 ++--
    fs/proc/thread_self.c | 6 +++---
    include/linux/pid_namespace.h | 4 +---
    include/linux/proc_fs.h | 2 ++
    6 files changed, 15 insertions(+), 14 deletions(-)

    diff --git a/fs/proc/base.c b/fs/proc/base.c
    index 672e71c52dbd..1eb366ad8b06 100644
    --- a/fs/proc/base.c
    +++ b/fs/proc/base.c
    @@ -3316,6 +3316,7 @@ static struct tgid_iter next_tgid(struct pid_namespace *ns, struct tgid_iter ite
    int proc_pid_readdir(struct file *file, struct dir_context *ctx)
    {
    struct tgid_iter iter;
    + struct proc_fs_info *fs_info = proc_sb_info(file_inode(file)->i_sb);
    struct pid_namespace *ns = proc_pid_ns(file_inode(file));
    loff_t pos = ctx->pos;

    @@ -3323,13 +3324,13 @@ 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 d449f095f0f7..637e26cc795e 100644
    --- a/fs/proc/root.c
    +++ b/fs/proc/root.c
    @@ -210,10 +210,10 @@ static void proc_kill_sb(struct super_block *sb)
    {
    struct proc_fs_info *fs_info = proc_sb_info(sb);

    - if (fs_info->pid_ns->proc_self)
    - dput(fs_info->pid_ns->proc_self);
    - if (fs_info->pid_ns->proc_thread_self)
    - dput(fs_info->pid_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(fs_info->pid_ns);
    kfree(fs_info);
    diff --git a/fs/proc/self.c b/fs/proc/self.c
    index 57c0a1047250..846fc2b7c8a8 100644
    --- a/fs/proc/self.c
    +++ b/fs/proc/self.c
    @@ -36,7 +36,7 @@ static unsigned self_inum __ro_after_init;
    int proc_setup_self(struct super_block *s)
    {
    struct inode *root_inode = d_inode(s->s_root);
    - struct pid_namespace *ns = proc_pid_ns(root_inode);
    + struct proc_fs_info *fs_info = proc_sb_info(s);
    struct dentry *self;
    int ret = -ENOMEM;

    @@ -62,7 +62,7 @@ int proc_setup_self(struct super_block *s)
    if (ret)
    pr_err("proc_fill_super: can't allocate /proc/self\n");
    else
    - ns->proc_self = self;
    + fs_info->proc_self = self;

    return ret;
    }
    diff --git a/fs/proc/thread_self.c b/fs/proc/thread_self.c
    index f61ae53533f5..2493cbbdfa6f 100644
    --- a/fs/proc/thread_self.c
    +++ b/fs/proc/thread_self.c
    @@ -36,7 +36,7 @@ static unsigned thread_self_inum __ro_after_init;
    int proc_setup_thread_self(struct super_block *s)
    {
    struct inode *root_inode = d_inode(s->s_root);
    - struct pid_namespace *ns = proc_pid_ns(root_inode);
    + struct proc_fs_info *fs_info = proc_sb_info(s);
    struct dentry *thread_self;
    int ret = -ENOMEM;

    @@ -60,9 +60,9 @@ int proc_setup_thread_self(struct super_block *s)
    inode_unlock(root_inode);

    if (ret)
    - pr_err("proc_fill_super: can't allocate /proc/thread_self\n");
    + pr_err("proc_fill_super: can't allocate /proc/thread-self\n");
    else
    - ns->proc_thread_self = thread_self;
    + fs_info->proc_thread_self = thread_self;

    return ret;
    }
    diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
    index 49538b172483..f91a8bf6e09e 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 2d79489e55aa..59162988998e 100644
    --- a/include/linux/proc_fs.h
    +++ b/include/linux/proc_fs.h
    @@ -14,6 +14,8 @@ struct seq_operations;

    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 */
    };

    static inline struct proc_fs_info *proc_sb_info(struct super_block *sb)
    --
    2.24.1
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