On 01/24, Denys Vlasenko wrote:
>
> This change makes __dentry_path() and d_path()
> immediately return ENAMETOOLONG if buflen < 2.
I am not sure about d_path, but as for __dentry_path:
> @@ -3122,13 +3125,14 @@ static char *__dentry_path(struct dentry *dentry,
> char *buf, int buflen)
> int len, seq = 0;
> int error = 0;
>
> + if (buflen < 2)
> + goto Elong;
> +
> rcu_read_lock();
> restart:
> end = buf + buflen;
> len = buflen;
> prepend(&end, &len, "\0", 1);
> - if (buflen < 1)
> - goto Elong;
you forgot to mention that this change fixes a bug, this "goto Elong"
leaks rcu_read_lock().
And probably you are right, the fix should be as simple as possible.
But can't we also simplify __dentry_path? Unless I missed something
we can move prepend() up, before rcu_read_lock(), "move Get '/' right"
into that prepend, and even kill retval... OK, most probably I missed
something, but at first glance we can do something like
static char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
{
int len, seq = 0;
int error = 0;
char *end;
buf += buflen;
/* Get '/' right, write "/\0" at the end */
if (prepend(&buf, &buflen, "/", 2))
goto Elong;
rcu_read_lock();
restart:
end = buf;
len = buflen;
read_seqbegin_or_lock(&rename_lock, &seq);
while (!IS_ROOT(dentry)) {
struct dentry *parent = dentry->d_parent;
int error;
prefetch(parent);
error = prepend_name(&end, &len, &dentry->d_name);
if (error)
break;
dentry = parent;
}
if (!(seq & 1))
rcu_read_unlock();
if (need_seqretry(&rename_lock, seq)) {
seq = 1;
goto restart;
}
done_seqretry(&rename_lock, seq);
if (!error)
return end;
Elong:
return ERR_PTR(-ENAMETOOLONG);
}
Oleg.
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