Commit e06689bf authored by Alexey Dobriyan's avatar Alexey Dobriyan Committed by Linus Torvalds
Browse files

proc: change ->nlink under proc_subdir_lock 

Currently gluing PDE into global /proc tree is done under lock, but
changing ->nlink is not.  Additionally struct proc_dir_entry::nlink is
not atomic so updates can be lost.

Link: http://lkml.kernel.org/r/20190925202436.GA17388@avx2


Signed-off-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3cde287b

fs/proc/generic.c

+15 −16
Original line number Diff line number Diff line
@@ -138,8 +138,12 @@ static int proc_getattr(const struct path *path, struct kstat *stat, 
{

	struct inode *inode = d_inode(path->dentry);

	struct proc_dir_entry *de = PDE(inode);

	if (de && de->nlink)

		set_nlink(inode, de->nlink);

	if (de) {

		nlink_t nlink = READ_ONCE(de->nlink);

		if (nlink > 0) {

			set_nlink(inode, nlink);

		}

	}



	generic_fillattr(inode, stat);

	return 0;
@@ -362,6 +366,7 @@ struct proc_dir_entry *proc_register(struct proc_dir_entry *dir, 
		write_unlock(&proc_subdir_lock);

		goto out_free_inum;

	}

	dir->nlink++;

	write_unlock(&proc_subdir_lock);



	return dp;
@@ -472,10 +477,7 @@ struct proc_dir_entry *proc_mkdir_data(const char *name, umode_t mode, 
		ent->data = data;

		ent->proc_fops = &proc_dir_operations;

		ent->proc_iops = &proc_dir_inode_operations;

		parent->nlink++;

		ent = proc_register(parent, ent);

		if (!ent)

			parent->nlink--;

	}

	return ent;

}
@@ -505,10 +507,7 @@ struct proc_dir_entry *proc_create_mount_point(const char *name) 
		ent->data = NULL;

		ent->proc_fops = NULL;

		ent->proc_iops = NULL;

		parent->nlink++;

		ent = proc_register(parent, ent);

		if (!ent)

			parent->nlink--;

	}

	return ent;

}
@@ -666,8 +665,12 @@ void remove_proc_entry(const char *name, struct proc_dir_entry *parent) 
	len = strlen(fn);



	de = pde_subdir_find(parent, fn, len);

	if (de)

	if (de) {

		rb_erase(&de->subdir_node, &parent->subdir);

		if (S_ISDIR(de->mode)) {

			parent->nlink--;

		}

	}

	write_unlock(&proc_subdir_lock);

	if (!de) {

		WARN(1, "name '%s'\n", name);
@@ -676,9 +679,6 @@ void remove_proc_entry(const char *name, struct proc_dir_entry *parent) 


	proc_entry_rundown(de);



	if (S_ISDIR(de->mode))

		parent->nlink--;

	de->nlink = 0;

	WARN(pde_subdir_first(de),

	     "%s: removing non-empty directory '%s/%s', leaking at least '%s'\n",

	     __func__, de->parent->name, de->name, pde_subdir_first(de)->name);
@@ -714,13 +714,12 @@ int remove_proc_subtree(const char *name, struct proc_dir_entry *parent) 
			de = next;

			continue;

		}

		write_unlock(&proc_subdir_lock);



		proc_entry_rundown(de);

		next = de->parent;

		if (S_ISDIR(de->mode))

			next->nlink--;

		de->nlink = 0;

		write_unlock(&proc_subdir_lock);



		proc_entry_rundown(de);

		if (de == root)

			break;

		pde_put(de);

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