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Commit 1bbc5513 authored by Al Viro's avatar Al Viro
Browse files

procfs: get rid of ancient BS in pid_revalidate() uses 



First of all, calling pid_revalidate() in the end of <pid>/* lookups
is *not* about closing any kind of races; that used to be true once
upon a time, but these days those comments are actively misleading.
Especially since pid_revalidate() doesn't even do d_drop() on
failure anymore.  It doesn't matter, anyway, since once
pid_revalidate() starts returning false, ->d_delete() of those
dentries starts saying "don't keep"; they won't get stuck in
dcache any longer than they are pinned.

These calls cannot be just removed, though - the side effect of
pid_revalidate() (updating i_uid/i_gid/etc.) is what we are calling
it for here.

Let's separate the "update ownership" into a new helper (pid_update_inode())
and use it, both in lookups and in pid_revalidate() itself.

The comments in pid_revalidate() are also out of date - they refer to
the time when pid_revalidate() used to call d_drop() directly...

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 11f17c9b

fs/proc/base.c

+24 −31
Original line number Diff line number Diff line
@@ -1803,15 +1803,22 @@ int pid_getattr(const struct path *path, struct kstat *stat, 
/* dentry stuff */



/*

 *	Exceptional case: normally we are not allowed to unhash a busy

 * directory. In this case, however, we can do it - no aliasing problems

 * due to the way we treat inodes.

 *

 * Set <pid>/... inode ownership (can change due to setuid(), etc.)

 */

void pid_update_inode(struct task_struct *task, struct inode *inode)

{

	task_dump_owner(task, inode->i_mode, &inode->i_uid, &inode->i_gid);



	inode->i_mode &= ~(S_ISUID | S_ISGID);

	security_task_to_inode(task, inode);

}



/*

 * Rewrite the inode's ownerships here because the owning task may have

 * performed a setuid(), etc.

 *

 */

int pid_revalidate(struct dentry *dentry, unsigned int flags)

static int pid_revalidate(struct dentry *dentry, unsigned int flags)

{

	struct inode *inode;

	struct task_struct *task;
@@ -1823,10 +1830,7 @@ int pid_revalidate(struct dentry *dentry, unsigned int flags) 
	task = get_proc_task(inode);



	if (task) {

		task_dump_owner(task, inode->i_mode, &inode->i_uid, &inode->i_gid);



		inode->i_mode &= ~(S_ISUID | S_ISGID);

		security_task_to_inode(task, inode);

		pid_update_inode(task, inode);

		put_task_struct(task);

		return 1;

	}
@@ -2438,7 +2442,7 @@ static int proc_pident_instantiate(struct inode *dir, 


	inode = proc_pid_make_inode(dir->i_sb, task, p->mode);

	if (!inode)

		goto out;

		return -ENOENT;



	ei = PROC_I(inode);

	if (S_ISDIR(inode->i_mode))
@@ -2448,13 +2452,10 @@ static int proc_pident_instantiate(struct inode *dir, 
	if (p->fop)

		inode->i_fop = p->fop;

	ei->op = p->op;

	pid_update_inode(task, inode);

	d_set_d_op(dentry, &pid_dentry_operations);

	d_add(dentry, inode);

	/* Close the race of the process dying before we return the dentry */

	if (pid_revalidate(dentry, 0))

	return 0;

out:

	return -ENOENT;

}



static struct dentry *proc_pident_lookup(struct inode *dir,
@@ -3140,22 +3141,18 @@ static int proc_pid_instantiate(struct inode *dir, 


	inode = proc_pid_make_inode(dir->i_sb, task, S_IFDIR | S_IRUGO | S_IXUGO);

	if (!inode)

		goto out;

		return -ENOENT;



	inode->i_op = &proc_tgid_base_inode_operations;

	inode->i_fop = &proc_tgid_base_operations;

	inode->i_flags|=S_IMMUTABLE;



	set_nlink(inode, nlink_tgid);

	pid_update_inode(task, inode);



	d_set_d_op(dentry, &pid_dentry_operations);



	d_add(dentry, inode);

	/* Close the race of the process dying before we return the dentry */

	if (pid_revalidate(dentry, 0))

	return 0;

out:

	return -ENOENT;

}



struct dentry *proc_pid_lookup(struct inode *dir, struct dentry * dentry, unsigned int flags)
@@ -3434,23 +3431,19 @@ static int proc_task_instantiate(struct inode *dir, 
{

	struct inode *inode;

	inode = proc_pid_make_inode(dir->i_sb, task, S_IFDIR | S_IRUGO | S_IXUGO);



	if (!inode)

		goto out;

		return -ENOENT;



	inode->i_op = &proc_tid_base_inode_operations;

	inode->i_fop = &proc_tid_base_operations;

	inode->i_flags |= S_IMMUTABLE;



	set_nlink(inode, nlink_tid);

	pid_update_inode(task, inode);



	d_set_d_op(dentry, &pid_dentry_operations);



	d_add(dentry, inode);

	/* Close the race of the process dying before we return the dentry */

	if (pid_revalidate(dentry, 0))

	return 0;

out:

	return -ENOENT;

}



static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry, unsigned int flags)

fs/proc/internal.h

+1 −1
Original line number Diff line number Diff line
@@ -147,7 +147,7 @@ extern const struct dentry_operations pid_dentry_operations; 
extern int pid_getattr(const struct path *, struct kstat *, u32, unsigned int);

extern int proc_setattr(struct dentry *, struct iattr *);

extern struct inode *proc_pid_make_inode(struct super_block *, struct task_struct *, umode_t);

extern int pid_revalidate(struct dentry *, unsigned int);

extern void pid_update_inode(struct task_struct *, struct inode *);

extern int pid_delete_dentry(const struct dentry *);

extern int proc_pid_readdir(struct file *, struct dir_context *);

extern struct dentry *proc_pid_lookup(struct inode *, struct dentry *, unsigned int);

fs/proc/namespaces.c

+3 −6
Original line number Diff line number Diff line
@@ -96,19 +96,16 @@ static int proc_ns_instantiate(struct inode *dir, 


	inode = proc_pid_make_inode(dir->i_sb, task, S_IFLNK | S_IRWXUGO);

	if (!inode)

		goto out;

		return -ENOENT;



	ei = PROC_I(inode);

	inode->i_op = &proc_ns_link_inode_operations;

	ei->ns_ops = ns_ops;

	pid_update_inode(task, inode);



	d_set_d_op(dentry, &pid_dentry_operations);

	d_add(dentry, inode);

	/* Close the race of the process dying before we return the dentry */

	if (pid_revalidate(dentry, 0))

	return 0;

out:

	return -ENOENT;

}



static int proc_ns_dir_readdir(struct file *file, struct dir_context *ctx)