From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:45648 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728512AbeK0UXL (ORCPT ); Tue, 27 Nov 2018 15:23:11 -0500 Date: Tue, 27 Nov 2018 10:25:51 +0100 From: Jan Kara To: Pan Bian Cc: Alexander Viro , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH V2] namei: free new_dentry late Message-ID: <20181127092551.GC16301@quack2.suse.cz> References: <1543104923-81192-1-git-send-email-bianpan2016@163.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1543104923-81192-1-git-send-email-bianpan2016@163.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Sun 25-11-18 08:15:23, Pan Bian wrote: > After calling dput(new_dentry), new_dentry is passed to fsnotify_move. > This may result in a use-after-free bug. This patch moves the put > operation late. > > Fixes: da1ce0670c14("vfs: add cross-rename") > Signed-off-by: Pan Bian The code is actually fine AFAICT. One new_dentry reference is passed into vfs_rename() and another one is acquired directly inside vfs_rename(). That is the one dropped early but there's still the original reference passed in protecting new_dentry from freeing. Am I missing something? Honza > --- > V2: correct the fixes commit information > --- > fs/namei.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/namei.c b/fs/namei.c > index 0cab649..8b104d9 100644 > --- a/fs/namei.c > +++ b/fs/namei.c > @@ -4498,7 +4498,6 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry, > unlock_two_nondirectories(source, target); > else if (target) > inode_unlock(target); > - dput(new_dentry); > if (!error) { > fsnotify_move(old_dir, new_dir, old_name.name, is_dir, > !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry); > @@ -4507,6 +4506,7 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry, > new_is_dir, NULL, new_dentry); > } > } > + dput(new_dentry); > release_dentry_name_snapshot(&old_name); > > return error; > -- > 2.7.4 > > -- Jan Kara SUSE Labs, CR