Re: [PATCH] autofs4: turn ->oz_pgrp into "struct pid *"

[Ian Kent <raven@themaw.net>]

On Sun, 2009-01-18 at 08:34 +0100, Oleg Nesterov wrote:
> Compile tested, please review, depends on
> 	pids-improve-get_task_pid-to-fix-the-unsafe-sys_wait4-task_pgrp.patch
> 
> Nowadays task_struct-> __session/__pgrp are writeonly, except task_pgrp_nr()
> is wrongly used by some filesystems, and autofs4 is the major offender.
> 
> Turn autofs_sb_info->oz_pgrp into "struct pid*" to make it namespace-friendly.

Yep, since "struct pid *" is namespace invariant this has to be the way
to go.

> 
> I guess autofs4_show_options()->pid_vnr() is not exactly right, but hopefully
> not worse than the current code.

But shouldn't pid_vnr(sbi->oz_pgrp) report the pid as seen in the
namespace of the calling process? In which case the only problem would
be listing the mount table from a subordinate namespace that cannot see
the process which did the mount, assuming fs namespace is not linked in
some strict way to pid namespace, this could give an odd result. What
might happen in this case Oleg?

> 
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> 
> --- CUR/fs/autofs4/autofs_i.h~2_AUTOFS4	2009-01-12 23:07:46.000000000 +0100
> +++ CUR/fs/autofs4/autofs_i.h	2009-01-18 06:51:07.000000000 +0100
> @@ -119,7 +119,7 @@ struct autofs_sb_info {
>  	u32 magic;
>  	int pipefd;
>  	struct file *pipe;
> -	pid_t oz_pgrp;
> +	struct pid *oz_pgrp;
>  	int catatonic;
>  	int version;
>  	int sub_version;
> @@ -153,7 +153,7 @@ static inline struct autofs_info *autofs
>     filesystem without "magic".) */
>  
>  static inline int autofs4_oz_mode(struct autofs_sb_info *sbi) {
> -	return sbi->catatonic || task_pgrp_nr(current) == sbi->oz_pgrp;
> +	return sbi->catatonic || task_pgrp(current) == sbi->oz_pgrp;
>  }
>  
>  /* Does a dentry have some pending activity? */
> --- CUR/fs/autofs4/dev-ioctl.c~2_AUTOFS4	2009-01-12 23:07:46.000000000 +0100
> +++ CUR/fs/autofs4/dev-ioctl.c	2009-01-18 07:34:05.000000000 +0100
> @@ -429,7 +429,8 @@ static int autofs_dev_ioctl_setpipefd(st
>  			fput(pipe);
>  			goto out;
>  		}
> -		sbi->oz_pgrp = task_pgrp_nr(current);
> +		put_pid(sbi->oz_pgrp);
> +		sbi->oz_pgrp = get_task_pid(current, PIDTYPE_PGID);
>  		sbi->pipefd = pipefd;
>  		sbi->pipe = pipe;
>  		sbi->catatonic = 0;
> --- CUR/fs/autofs4/inode.c~2_AUTOFS4	2009-01-12 23:07:46.000000000 +0100
> +++ CUR/fs/autofs4/inode.c	2009-01-18 07:44:28.000000000 +0100
> @@ -172,6 +172,7 @@ void autofs4_kill_sb(struct super_block 
>  	autofs4_force_release(sbi);
>  
>  	sb->s_fs_info = NULL;
> +	put_pid(sbi->oz_pgrp);
>  	kfree(sbi);
>  
>  out_kill_sb:
> @@ -192,7 +193,7 @@ static int autofs4_show_options(struct s
>  		seq_printf(m, ",uid=%u", root_inode->i_uid);
>  	if (root_inode->i_gid != 0)
>  		seq_printf(m, ",gid=%u", root_inode->i_gid);
> -	seq_printf(m, ",pgrp=%d", sbi->oz_pgrp);
> +	seq_printf(m, ",pgrp=%d", pid_vnr(sbi->oz_pgrp));
>  	seq_printf(m, ",timeout=%lu", sbi->exp_timeout/HZ);
>  	seq_printf(m, ",minproto=%d", sbi->min_proto);
>  	seq_printf(m, ",maxproto=%d", sbi->max_proto);
> @@ -229,7 +230,8 @@ static const match_table_t tokens = {
>  };
>  
>  static int parse_options(char *options, int *pipefd, uid_t *uid, gid_t *gid,
> -		pid_t *pgrp, unsigned int *type, int *minproto, int *maxproto)
> +			 struct pid **pgrp, unsigned int *type, int *minproto,
> +			 int *maxproto)
>  {
>  	char *p;
>  	substring_t args[MAX_OPT_ARGS];
> @@ -237,7 +239,6 @@ static int parse_options(char *options, 
>  
>  	*uid = current_uid();
>  	*gid = current_gid();
> -	*pgrp = task_pgrp_nr(current);
>  
>  	*minproto = AUTOFS_MIN_PROTO_VERSION;
>  	*maxproto = AUTOFS_MAX_PROTO_VERSION;
> @@ -271,7 +272,9 @@ static int parse_options(char *options, 
>  		case Opt_pgrp:
>  			if (match_int(args, &option))
>  				return 1;
> -			*pgrp = option;
> +			*pgrp = find_get_pid(option);
> +			if (!*pgrp)
> +				return 1;
>  			break;
>  		case Opt_minproto:
>  			if (match_int(args, &option))
> @@ -296,6 +299,10 @@ static int parse_options(char *options, 
>  			return 1;
>  		}
>  	}
> +
> +	if (!*pgrp)
> +		*pgrp = get_task_pid(current, PIDTYPE_PGID);
> +
>  	return (*pipefd < 0);
>  }
>  
> @@ -334,7 +341,6 @@ int autofs4_fill_super(struct super_bloc
>  	sbi->pipe = NULL;
>  	sbi->catatonic = 1;
>  	sbi->exp_timeout = 0;
> -	sbi->oz_pgrp = task_pgrp_nr(current);
>  	sbi->sb = s;
>  	sbi->version = 0;
>  	sbi->sub_version = 0;
> @@ -401,7 +407,7 @@ int autofs4_fill_super(struct super_bloc
>  		sbi->version = sbi->max_proto;
>  	sbi->sub_version = AUTOFS_PROTO_SUBVERSION;
>  
> -	DPRINTK("pipe fd = %d, pgrp = %u", pipefd, sbi->oz_pgrp);
> +	DPRINTK("pipe fd = %d, pgrp = %u", pipefd, pid_vnr(sbi->oz_pgrp));
>  	pipe = fget(pipefd);
>  	
>  	if (!pipe) {
> @@ -436,6 +442,7 @@ fail_iput:
>  fail_ino:
>  	kfree(ino);
>  fail_free:
> +	put_pid(sbi->oz_pgrp);
>  	kfree(sbi);
>  	s->s_fs_info = NULL;
>  fail_unlock:
> --- CUR/fs/autofs4/root.c~2_AUTOFS4	2008-10-10 00:13:53.000000000 +0200
> +++ CUR/fs/autofs4/root.c	2009-01-18 08:09:35.000000000 +0100
> @@ -483,7 +483,7 @@ static struct dentry *autofs4_lookup(str
>  	oz_mode = autofs4_oz_mode(sbi);
>  
>  	DPRINTK("pid = %u, pgrp = %u, catatonic = %d, oz_mode = %d",
> -		 current->pid, task_pgrp_nr(current), sbi->catatonic, oz_mode);
> +		 current->pid, task_pgrp_vnr(current), sbi->catatonic, oz_mode);
>  
>  	expiring = autofs4_lookup_expiring(sbi, dentry->d_parent, &dentry->d_name);
>  	if (expiring) {
> @@ -877,7 +877,7 @@ static int autofs4_root_ioctl(struct ino
>  	void __user *p = (void __user *)arg;
>  
>  	DPRINTK("cmd = 0x%08x, arg = 0x%08lx, sbi = %p, pgrp = %u",
> -		cmd,arg,sbi,task_pgrp_nr(current));
> +		cmd, arg, sbi, task_pgrp_vnr(current));
>  
>  	if (_IOC_TYPE(cmd) != _IOC_TYPE(AUTOFS_IOC_FIRST) ||
>  	     _IOC_NR(cmd) - _IOC_NR(AUTOFS_IOC_FIRST) >= AUTOFS_IOC_COUNT)
>