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From:   ebiederm@xmission.com (Eric W. Biederman)
To:     Alexey Gladkov <gladkov.alexey@gmail.com>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        syzbot <syzbot+c1af344512918c61362c@syzkaller.appspotmail.com>,
        jmorris@namei.org, linux-next@vger.kernel.org,
        linux-security-module@vger.kernel.org, serge@hallyn.com,
        sfr@canb.auug.org.au, syzkaller-bugs@googlegroups.com,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>
References: <87lfltcbc4.fsf@x220.int.ebiederm.org>
        <20200518111716.2896385-1-gladkov.alexey@gmail.com>
Date:   Mon, 18 May 2020 07:08:57 -0500
In-Reply-To: <20200518111716.2896385-1-gladkov.alexey@gmail.com> (Alexey
        Gladkov's message of "Mon, 18 May 2020 13:17:16 +0200")
Message-ID: <871rnh78di.fsf@x220.int.ebiederm.org>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux)
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Subject: Re: [PATCH v2] proc: proc_pid_ns takes super_block as an argument
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Alexey Gladkov <gladkov.alexey@gmail.com> writes:

> The proc_pid_ns() can be used for both inode and dentry. To avoid making
> two identical functions, change the argument type of the proc_pid_ns().
>
> Link: https://lore.kernel.org/lkml/c3461e26-1407-2262-c709-dac0df3da2d0@i-love.sakura.ne.jp/
> Reported-by: syzbot+c1af344512918c61362c@syzkaller.appspotmail.com
> Signed-off-by: Alexey Gladkov <gladkov.alexey@gmail.com>

So overall this looks good.

However, the description leaves a little bit to be desired as it does
not describe why it is bad to use dentry->d_sb.  A fixes tag would be
nice if for no other reason than to help anyone who decides to backport
this.

And can you please compile test this?

There is a very silly typo in proc that keeps this from compiling.

Thank you,
Eric

> ---
>  fs/locks.c                 |  4 ++--
>  fs/proc/array.c            |  2 +-
>  fs/proc/base.c             | 10 +++++-----
>  fs/proc/self.c             |  2 +-
>  fs/proc/thread_self.c      |  2 +-
>  include/linux/proc_fs.h    |  4 ++--
>  kernel/fork.c              |  2 +-
>  net/ipv6/ip6_flowlabel.c   |  2 +-
>  security/tomoyo/realpath.c |  2 +-
>  9 files changed, 15 insertions(+), 15 deletions(-)
>
> diff --git a/fs/locks.c b/fs/locks.c
> index 399c5dbb72c4..ab702d6efb55 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -2823,7 +2823,7 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl,
>  {
>  	struct inode *inode = NULL;
>  	unsigned int fl_pid;
> -	struct pid_namespace *proc_pidns = proc_pid_ns(file_inode(f->file));
> +	struct pid_namespace *proc_pidns = proc_pid_ns(file_inode(f->file)->i_sb);
>  
>  	fl_pid = locks_translate_pid(fl, proc_pidns);
>  	/*
> @@ -2901,7 +2901,7 @@ static int locks_show(struct seq_file *f, void *v)
>  {
>  	struct locks_iterator *iter = f->private;
>  	struct file_lock *fl, *bfl;
> -	struct pid_namespace *proc_pidns = proc_pid_ns(file_inode(f->file));
> +	struct pid_namespace *proc_pidns = proc_pid_ns(file_inode(f->file)->i_sb);
>  
>  	fl = hlist_entry(v, struct file_lock, fl_link);
>  
> diff --git a/fs/proc/array.c b/fs/proc/array.c
> index 8e16f14bb05a..a4d4763731e0 100644
> --- a/fs/proc/array.c
> +++ b/fs/proc/array.c
> @@ -728,7 +728,7 @@ static int children_seq_show(struct seq_file *seq, void *v)
>  {
>  	struct inode *inode = file_inode(seq->file);
>  
> -	seq_printf(seq, "%d ", pid_nr_ns(v, proc_pid_ns(inode)));
> +	seq_printf(seq, "%d ", pid_nr_ns(v, proc_pid_ns(inode)->i_sb));
>  	return 0;
>  }
>  
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 5a307b3bb2d1..30c9fceca0b7 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -754,7 +754,7 @@ static const struct inode_operations proc_def_inode_operations = {
>  static int proc_single_show(struct seq_file *m, void *v)
>  {
>  	struct inode *inode = m->private;
> -	struct pid_namespace *ns = proc_pid_ns(inode);
> +	struct pid_namespace *ns = proc_pid_ns(inode->i_sb);
>  	struct pid *pid = proc_pid(inode);
>  	struct task_struct *task;
>  	int ret;
> @@ -1423,7 +1423,7 @@ static const struct file_operations proc_fail_nth_operations = {
>  static int sched_show(struct seq_file *m, void *v)
>  {
>  	struct inode *inode = m->private;
> -	struct pid_namespace *ns = proc_pid_ns(inode);
> +	struct pid_namespace *ns = proc_pid_ns(inode->i_sb);
>  	struct task_struct *p;
>  
>  	p = get_proc_task(inode);
> @@ -2466,7 +2466,7 @@ static int proc_timers_open(struct inode *inode, struct file *file)
>  		return -ENOMEM;
>  
>  	tp->pid = proc_pid(inode);
> -	tp->ns = proc_pid_ns(inode);
> +	tp->ns = proc_pid_ns(inode->i_sb);
>  	return 0;
>  }
>  
> @@ -3377,7 +3377,7 @@ 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));
> +	struct pid_namespace *ns = proc_pid_ns(file_inode(file)->i_sb);
>  	loff_t pos = ctx->pos;
>  
>  	if (pos >= PID_MAX_LIMIT + TGID_OFFSET)
> @@ -3730,7 +3730,7 @@ static int proc_task_readdir(struct file *file, struct dir_context *ctx)
>  	/* f_version caches the tgid value that the last readdir call couldn't
>  	 * return. lseek aka telldir automagically resets f_version to 0.
>  	 */
> -	ns = proc_pid_ns(inode);
> +	ns = proc_pid_ns(inode->i_sb);
>  	tid = (int)file->f_version;
>  	file->f_version = 0;
>  	for (task = first_tid(proc_pid(inode), tid, ctx->pos - 2, ns);
> diff --git a/fs/proc/self.c b/fs/proc/self.c
> index 309301ac0136..ca5158fa561c 100644
> --- a/fs/proc/self.c
> +++ b/fs/proc/self.c
> @@ -12,7 +12,7 @@ static const char *proc_self_get_link(struct dentry *dentry,
>  				      struct inode *inode,
>  				      struct delayed_call *done)
>  {
> -	struct pid_namespace *ns = proc_pid_ns(inode);
> +	struct pid_namespace *ns = proc_pid_ns(inode->i_sb);
>  	pid_t tgid = task_tgid_nr_ns(current, ns);
>  	char *name;
>  
> diff --git a/fs/proc/thread_self.c b/fs/proc/thread_self.c
> index 2493cbbdfa6f..ac284f409568 100644
> --- a/fs/proc/thread_self.c
> +++ b/fs/proc/thread_self.c
> @@ -12,7 +12,7 @@ static const char *proc_thread_self_get_link(struct dentry *dentry,
>  					     struct inode *inode,
>  					     struct delayed_call *done)
>  {
> -	struct pid_namespace *ns = proc_pid_ns(inode);
> +	struct pid_namespace *ns = proc_pid_ns(inode->i_sb);
>  	pid_t tgid = task_tgid_nr_ns(current, ns);
>  	pid_t pid = task_pid_nr_ns(current, ns);
>  	char *name;
> diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
> index 2cb424e6f36a..6ec524d8842c 100644
> --- a/include/linux/proc_fs.h
> +++ b/include/linux/proc_fs.h
> @@ -202,9 +202,9 @@ int open_related_ns(struct ns_common *ns,
>  		   struct ns_common *(*get_ns)(struct ns_common *ns));
>  
>  /* get the associated pid namespace for a file in procfs */
> -static inline struct pid_namespace *proc_pid_ns(const struct inode *inode)
> +static inline struct pid_namespace *proc_pid_ns(struct super_block *sb)
>  {
> -	return proc_sb_info(inode->i_sb)->pid_ns;
> +	return proc_sb_info(sb)->pid_ns;
>  }
>  
>  #endif /* _LINUX_PROC_FS_H */
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 4385f3d639f2..e7bdaccad942 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1745,7 +1745,7 @@ static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
>  	pid_t nr = -1;
>  
>  	if (likely(pid_has_task(pid, PIDTYPE_PID))) {
> -		ns = proc_pid_ns(file_inode(m->file));
> +		ns = proc_pid_ns(file_inode(m->file)->i_sb);
>  		nr = pid_nr_ns(pid, ns);
>  	}
>  
> diff --git a/net/ipv6/ip6_flowlabel.c b/net/ipv6/ip6_flowlabel.c
> index d64b83e85642..ce4fbba4acce 100644
> --- a/net/ipv6/ip6_flowlabel.c
> +++ b/net/ipv6/ip6_flowlabel.c
> @@ -779,7 +779,7 @@ static void *ip6fl_seq_start(struct seq_file *seq, loff_t *pos)
>  {
>  	struct ip6fl_iter_state *state = ip6fl_seq_private(seq);
>  
> -	state->pid_ns = proc_pid_ns(file_inode(seq->file));
> +	state->pid_ns = proc_pid_ns(file_inode(seq->file)->i_sb);
>  
>  	rcu_read_lock_bh();
>  	return *pos ? ip6fl_get_idx(seq, *pos - 1) : SEQ_START_TOKEN;
> diff --git a/security/tomoyo/realpath.c b/security/tomoyo/realpath.c
> index 08b096e2f7e3..df4798980416 100644
> --- a/security/tomoyo/realpath.c
> +++ b/security/tomoyo/realpath.c
> @@ -162,7 +162,7 @@ static char *tomoyo_get_local_path(struct dentry *dentry, char * const buffer,
>  	if (sb->s_magic == PROC_SUPER_MAGIC && *pos == '/') {
>  		char *ep;
>  		const pid_t pid = (pid_t) simple_strtoul(pos + 1, &ep, 10);
> -		struct pid_namespace *proc_pidns = proc_pid_ns(d_inode(dentry));
> +		struct pid_namespace *proc_pidns = proc_pid_ns(sb);
>  
>  		if (*ep == '/' && pid && pid ==
>  		    task_tgid_nr_ns(current, proc_pidns)) {