From: Matthew Wilcox <willy@infradead.org>
To: Eric Biggers <ebiggers@kernel.org>
Cc: Tiezhu Yang <yangtiezhu@loongson.cn>,
Alexander Viro <viro@zeniv.linux.org.uk>,
"Theodore Y. Ts'o" <tytso@mit.edu>,
Jaegeuk Kim <jaegeuk@kernel.org>, Chao Yu <yuchao0@huawei.com>,
Tyler Hicks <tyhicks@canonical.com>,
linux-fsdevel@vger.kernel.org, ecryptfs@vger.kernel.org,
linux-fscrypt@vger.kernel.org,
linux-f2fs-devel@lists.sourceforge.net,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4] fs: introduce is_dot_or_dotdot helper for cleanup
Date: Thu, 12 Dec 2019 10:13:02 -0800 [thread overview]
Message-ID: <20191212181302.GT32169@bombadil.infradead.org> (raw)
In-Reply-To: <20191210191912.GA99557@gmail.com>
On Tue, Dec 10, 2019 at 11:19:13AM -0800, Eric Biggers wrote:
> > +static inline bool is_dot_or_dotdot(const unsigned char *name, size_t len)
> > +{
> > + if (unlikely(name[0] == '.')) {
> > + if (len < 2 || (len == 2 && name[1] == '.'))
> > + return true;
> > + }
> > +
> > + return false;
> > +}
>
> This doesn't handle the len=0 case. Did you check that none of the users pass
> in zero-length names? It looks like fscrypt_fname_disk_to_usr() can, if the
> directory entry on-disk has a zero-length name. Currently it will return
> -EUCLEAN in that case, but with this patch it may think it's the name ".".
Trying to wrench this back on track ...
fscrypt_fname_disk_to_usr is called by:
fscrypt_get_symlink():
if (cstr.len == 0)
return ERR_PTR(-EUCLEAN);
ext4_readdir():
Does not currently check de->name_len. I believe this check should
be added to __ext4_check_dir_entry() because a zero-length directory
entry can affect both encrypted and non-encrypted directory entries.
dx_show_leaf():
Same as ext4_readdir(). Should probably call ext4_check_dir_entry()?
htree_dirblock_to_tree():
Would be covered by a fix to ext4_check_dir_entry().
f2fs_fill_dentries():
if (de->name_len == 0) {
...
ubifs_readdir():
Does not currently check de->name_len. Also affects non-encrypted
directory entries.
So of the six callers, two of them already check the dirent length for
being zero, and four of them ought to anyway, but don't. I think they
should be fixed, but clearly we don't historically check for this kind
of data corruption (strangely), so I don't think that's a reason to hold
up this patch until the individual filesystems are fixed.
next prev parent reply other threads:[~2019-12-12 18:13 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-10 12:10 [PATCH v4] fs: introduce is_dot_or_dotdot helper for cleanup Tiezhu Yang
2019-12-10 12:13 ` Matthew Wilcox
2019-12-10 19:19 ` Eric Biggers
2019-12-10 23:10 ` Al Viro
2019-12-11 0:56 ` Tiezhu Yang
2019-12-12 18:13 ` Matthew Wilcox [this message]
[not found] <20200128221112.GA30200@bombadil.infradead.org>
2020-01-29 1:23 ` Andreas Dilger
2020-01-29 7:36 ` Matthew Wilcox
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