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Commit 6bb41321 authored by Ivan Delalande's avatar Ivan Delalande Committed by Greg Kroah-Hartman
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proc/sysctl: don't return ENOMEM on lookup when a table is unregistering 



commit ea5751ccd665a2fd1b24f9af81f6167f0718c5f6 upstream.

proc_sys_lookup can fail with ENOMEM instead of ENOENT when the
corresponding sysctl table is being unregistered. In our case we see
this upon opening /proc/sys/net/*/conf files while network interfaces
are being deleted, which confuses our configuration daemon.

The problem was successfully reproduced and this fix tested on v4.9.122
and v4.20-rc6.

v2: return ERR_PTRs in all cases when proc_sys_make_inode fails instead
of mixing them with NULL. Thanks Al Viro for the feedback.

Fixes: ace0c791 ("proc/sysctl: Don't grab i_lock under sysctl_lock.")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarIvan Delalande <colona@arista.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 488f2c66

fs/proc/proc_sysctl.c

+6 −7
Original line number Diff line number Diff line
@@ -464,7 +464,7 @@ static struct inode *proc_sys_make_inode(struct super_block *sb, 


	inode = new_inode(sb);

	if (!inode)

		goto out;

		return ERR_PTR(-ENOMEM);



	inode->i_ino = get_next_ino();
@@ -474,8 +474,7 @@ static struct inode *proc_sys_make_inode(struct super_block *sb, 
	if (unlikely(head->unregistering)) {

		spin_unlock(&sysctl_lock);

		iput(inode);

		inode = NULL;

		goto out;

		return ERR_PTR(-ENOENT);

	}

	ei->sysctl = head;

	ei->sysctl_entry = table;
@@ -500,7 +499,6 @@ static struct inode *proc_sys_make_inode(struct super_block *sb, 
	if (root->set_ownership)

		root->set_ownership(head, table, &inode->i_uid, &inode->i_gid);



out:

	return inode;

}
@@ -549,10 +547,11 @@ static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry, 
			goto out;

	}



	err = ERR_PTR(-ENOMEM);

	inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p);

	if (!inode)

	if (IS_ERR(inode)) {

		err = ERR_CAST(inode);

		goto out;

	}



	d_set_d_op(dentry, &proc_sys_dentry_operations);

	err = d_splice_alias(inode, dentry);
@@ -685,7 +684,7 @@ static bool proc_sys_fill_cache(struct file *file, 
		if (d_in_lookup(child)) {

			struct dentry *res;

			inode = proc_sys_make_inode(dir->d_sb, head, table);

			if (!inode) {

			if (IS_ERR(inode)) {

				d_lookup_done(child);

				dput(child);

				return false;