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bh=4WxAQadBsZpy3zOHCcC+EBnliJOW3HQ1p2Dl1lHUVn8=; b=OakK/kTzXMSGMAJw5OudJ4DuZP 3ZPiA47VEeorbeigTp8Xs4wMXkHawcfKq8H1roqSXHufyiUpJqyU42JwJqRWTPEgA7LBOHenPxlYN U6r/idGXChdIrkuIdnm3VFzpZIA+PU/jdcje6RBy/YWRXO0jW2tCgElhQItrFM+ov7aY=; Received: from mail.kernel.org ([198.145.29.99]) by sfi-mx-3.v28.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.92.2) id 1kfILZ-002tm8-Ex for linux-f2fs-devel@lists.sourceforge.net; Wed, 18 Nov 2020 07:57:58 +0000 Received: from sol.attlocal.net (172-10-235-113.lightspeed.sntcca.sbcglobal.net [172.10.235.113]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A66B020872; Wed, 18 Nov 2020 07:57:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605686260; bh=FigGyYGVqyexbkViWFXWCBw61iVGnXUSTYihGGdmkRE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eRCSgvfsCg1QTVP5X/naFr2Dfarwmp41S1fV43iSP/OjrT5qpwoEiibmVfG5qqCO1 Od3miTUeHxuE84xOTJx12qGLmh570Us2zeO5b5g/bqB7xJYav4yunwirLCZJXForrW Q7EW77lq7oHivyoQyvlOM136mx+VhyJg8ZMYengk= From: Eric Biggers To: linux-fscrypt@vger.kernel.org Date: Tue, 17 Nov 2020 23:56:05 -0800 Message-Id: <20201118075609.120337-2-ebiggers@kernel.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201118075609.120337-1-ebiggers@kernel.org> References: <20201118075609.120337-1-ebiggers@kernel.org> MIME-Version: 1.0 X-Headers-End: 1kfILZ-002tm8-Ex Subject: [f2fs-dev] [PATCH 1/5] fscrypt: add fscrypt_is_nokey_name() X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-mtd@lists.infradead.org, stable@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net From: Eric Biggers It's possible to create a duplicate filename in an encrypted directory by creating a file concurrently with adding the encryption key. Specifically, sys_open(O_CREAT) (or sys_mkdir(), sys_mknod(), or sys_symlink()) can lookup the target filename while the directory's encryption key hasn't been added yet, resulting in a negative no-key dentry. The VFS then calls ->create() (or ->mkdir(), ->mknod(), or ->symlink()) because the dentry is negative. Normally, ->create() would return -ENOKEY due to the directory's key being unavailable. However, if the key was added between the dentry lookup and ->create(), then the filesystem will go ahead and try to create the file. If the target filename happens to already exist as a normal name (not a no-key name), a duplicate filename may be added to the directory. In order to fix this, we need to fix the filesystems to prevent ->create(), ->mkdir(), ->mknod(), and ->symlink() on no-key names. (->rename() and ->link() need it too, but those are already handled correctly by fscrypt_prepare_rename() and fscrypt_prepare_link().) In preparation for this, add a helper function fscrypt_is_nokey_name() that filesystems can use to do this check. Use this helper function for the existing checks that fs/crypto/ does for rename and link. Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers --- fs/crypto/hooks.c | 5 +++-- include/linux/fscrypt.h | 34 ++++++++++++++++++++++++++++++++++ 2 files changed, 37 insertions(+), 2 deletions(-) diff --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c index 20b0df47fe6a..061418be4b08 100644 --- a/fs/crypto/hooks.c +++ b/fs/crypto/hooks.c @@ -61,7 +61,7 @@ int __fscrypt_prepare_link(struct inode *inode, struct inode *dir, return err; /* ... in case we looked up no-key name before key was added */ - if (dentry->d_flags & DCACHE_NOKEY_NAME) + if (fscrypt_is_nokey_name(dentry)) return -ENOKEY; if (!fscrypt_has_permitted_context(dir, inode)) @@ -86,7 +86,8 @@ int __fscrypt_prepare_rename(struct inode *old_dir, struct dentry *old_dentry, return err; /* ... in case we looked up no-key name(s) before key was added */ - if ((old_dentry->d_flags | new_dentry->d_flags) & DCACHE_NOKEY_NAME) + if (fscrypt_is_nokey_name(old_dentry) || + fscrypt_is_nokey_name(new_dentry)) return -ENOKEY; if (old_dir != new_dir) { diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h index a8f7a43f031b..8e1d31c959bf 100644 --- a/include/linux/fscrypt.h +++ b/include/linux/fscrypt.h @@ -111,6 +111,35 @@ static inline void fscrypt_handle_d_move(struct dentry *dentry) dentry->d_flags &= ~DCACHE_NOKEY_NAME; } +/** + * fscrypt_is_nokey_name() - test whether a dentry is a no-key name + * @dentry: the dentry to check + * + * This returns true if the dentry is a no-key dentry. A no-key dentry is a + * dentry that was created in an encrypted directory that hasn't had its + * encryption key added yet. Such dentries may be either positive or negative. + * + * When a filesystem is asked to create a new filename in an encrypted directory + * and the new filename's dentry is a no-key dentry, it must fail the operation + * with ENOKEY. This includes ->create(), ->mkdir(), ->mknod(), ->symlink(), + * ->rename(), and ->link(). (However, ->rename() and ->link() are already + * handled by fscrypt_prepare_rename() and fscrypt_prepare_link().) + * + * This is necessary because creating a filename requires the directory's + * encryption key, but just checking for the key on the directory inode during + * the final filesystem operation doesn't guarantee that the key was available + * during the preceding dentry lookup. And the key must have already been + * available during the dentry lookup in order for it to have been checked + * whether the filename already exists in the directory and for the new file's + * dentry not to be invalidated due to it incorrectly having the no-key flag. + * + * Return: %true if the dentry is a no-key name + */ +static inline bool fscrypt_is_nokey_name(const struct dentry *dentry) +{ + return dentry->d_flags & DCACHE_NOKEY_NAME; +} + /* crypto.c */ void fscrypt_enqueue_decrypt_work(struct work_struct *); @@ -244,6 +273,11 @@ static inline void fscrypt_handle_d_move(struct dentry *dentry) { } +static inline bool fscrypt_is_nokey_name(const struct dentry *dentry) +{ + return false; +} + /* crypto.c */ static inline void fscrypt_enqueue_decrypt_work(struct work_struct *work) { -- 2.29.2 _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel