From: Al Viro <viro@zeniv.linux.org.uk>
To: Liangyan <liangyan.peng@linux.alibaba.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>,
linux-unionfs@vger.kernel.org, linux-kernel@vger.kernel.org,
joseph.qi@linux.alibaba.com
Subject: Re: [PATCH v2] ovl: fix dentry leak in ovl_get_redirect
Date: Mon, 21 Dec 2020 06:26:53 +0000 [thread overview]
Message-ID: <20201221062653.GO3579531@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20201220120927.115232-1-liangyan.peng@linux.alibaba.com>
On Sun, Dec 20, 2020 at 08:09:27PM +0800, Liangyan wrote:
> +++ b/fs/overlayfs/dir.c
> @@ -973,6 +973,7 @@ static char *ovl_get_redirect(struct dentry *dentry, bool abs_redirect)
> for (d = dget(dentry); !IS_ROOT(d);) {
> const char *name;
> int thislen;
> + struct dentry *parent = NULL;
>
> spin_lock(&d->d_lock);
> name = ovl_dentry_get_redirect(d);
> @@ -992,7 +993,22 @@ static char *ovl_get_redirect(struct dentry *dentry, bool abs_redirect)
>
> buflen -= thislen;
> memcpy(&buf[buflen], name, thislen);
> - tmp = dget_dlock(d->d_parent);
> + parent = d->d_parent;
> + if (unlikely(!spin_trylock(&parent->d_lock))) {
> + rcu_read_lock();
> + spin_unlock(&d->d_lock);
> +again:
> + parent = READ_ONCE(d->d_parent);
> + spin_lock(&parent->d_lock);
> + if (unlikely(parent != d->d_parent)) {
> + spin_unlock(&parent->d_lock);
> + goto again;
> + }
> + rcu_read_unlock();
> + spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
> + }
> + tmp = dget_dlock(parent);
> + spin_unlock(&parent->d_lock);
> spin_unlock(&d->d_lock);
Yecchhhh.... What's wrong with just doing
spin_unlock(&d->d_lock);
parent = dget_parent(d);
dput(d);
d = parent;
instead of that?
next prev parent reply other threads:[~2020-12-21 6:27 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-20 12:09 [PATCH v2] ovl: fix dentry leak in ovl_get_redirect Liangyan
2020-12-21 6:14 ` Liangyan
2020-12-21 6:26 ` Al Viro [this message]
2020-12-21 11:14 ` Joseph Qi
2020-12-21 12:11 ` Al Viro
2020-12-21 16:51 ` Liangyan
2020-12-21 17:35 ` Al Viro
2020-12-21 18:15 ` Liangyan
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