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proc/sysctl: don't return ENOMEM on lookup when a table is unregistering 

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: ace0c791e6 ("proc/sysctl: Don't grab i_lock under sysctl_lock.")
Cc: stable@vger.kernel.org
Signed-off-by: Ivan Delalande <colona@arista.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Ivan Delalande 2018-12-13 15:20:52 -08:00 committed by Al Viro
parent 0afa996483
commit ea5751ccd6
1 changed files with 6 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
fs/proc/proc_sysctl.c
View File

@ -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;