This is a note to let you know that I've just added the patch titled ext4 crypto: revalidate dentry after adding or removing the key to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: ext4-crypto-revalidate-dentry-after-adding-or-removing-the-key.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 28b4c263961c47da84ed8b5be0b5116bad1133eb Mon Sep 17 00:00:00 2001 From: Theodore Ts'o <tytso@xxxxxxx> Date: Sun, 7 Feb 2016 19:35:05 -0500 Subject: ext4 crypto: revalidate dentry after adding or removing the key From: Theodore Ts'o <tytso@xxxxxxx> commit 28b4c263961c47da84ed8b5be0b5116bad1133eb upstream. Add a validation check for dentries for encrypted directory to make sure we're not caching stale data after a key has been added or removed. Also check to make sure that status of the encryption key is updated when readdir(2) is executed. Signed-off-by: Theodore Ts'o <tytso@xxxxxxx> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/ext4/crypto.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++ fs/ext4/dir.c | 6 ++++++ fs/ext4/ext4.h | 1 + fs/ext4/namei.c | 18 ++++++++++++++++++ 4 files changed, 75 insertions(+) --- a/fs/ext4/crypto.c +++ b/fs/ext4/crypto.c @@ -469,3 +469,53 @@ uint32_t ext4_validate_encryption_key_si return size; return 0; } + +/* + * Validate dentries for encrypted directories to make sure we aren't + * potentially caching stale data after a key has been added or + * removed. + */ +static int ext4_d_revalidate(struct dentry *dentry, unsigned int flags) +{ + struct inode *dir = d_inode(dentry->d_parent); + struct ext4_crypt_info *ci = EXT4_I(dir)->i_crypt_info; + int dir_has_key, cached_with_key; + + if (!ext4_encrypted_inode(dir)) + return 0; + + /* this should eventually be an flag in d_flags */ + cached_with_key = dentry->d_fsdata != NULL; + dir_has_key = (ci != NULL); + + /* + * If the dentry was cached without the key, and it is a + * negative dentry, it might be a valid name. We can't check + * if the key has since been made available due to locking + * reasons, so we fail the validation so ext4_lookup() can do + * this check. + * + * We also fail the validation if the dentry was created with + * the key present, but we no longer have the key, or vice versa. + */ + if ((!cached_with_key && d_is_negative(dentry)) || + (!cached_with_key && dir_has_key) || + (cached_with_key && !dir_has_key)) { +#if 0 /* Revalidation debug */ + char buf[80]; + char *cp = simple_dname(dentry, buf, sizeof(buf)); + + if (IS_ERR(cp)) + cp = (char *) "???"; + pr_err("revalidate: %s %p %d %d %d\n", cp, dentry->d_fsdata, + cached_with_key, d_is_negative(dentry), + dir_has_key); +#endif + return 0; + } + return 1; +} + +const struct dentry_operations ext4_encrypted_d_ops = { + .d_revalidate = ext4_d_revalidate, +}; --- a/fs/ext4/dir.c +++ b/fs/ext4/dir.c @@ -111,6 +111,12 @@ static int ext4_readdir(struct file *fil int dir_has_error = 0; struct ext4_str fname_crypto_str = {.name = NULL, .len = 0}; + if (ext4_encrypted_inode(inode)) { + err = ext4_get_encryption_info(inode); + if (err && err != -ENOKEY) + return err; + } + if (is_dx_dir(inode)) { err = ext4_dx_readdir(file, ctx); if (err != ERR_BAD_DX_DIR) { --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -2268,6 +2268,7 @@ struct page *ext4_encrypt(struct inode * struct page *plaintext_page); int ext4_decrypt(struct page *page); int ext4_encrypted_zeroout(struct inode *inode, struct ext4_extent *ex); +extern const struct dentry_operations ext4_encrypted_d_ops; #ifdef CONFIG_EXT4_FS_ENCRYPTION int ext4_init_crypto(void); --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -1557,6 +1557,24 @@ static struct dentry *ext4_lookup(struct struct ext4_dir_entry_2 *de; struct buffer_head *bh; + if (ext4_encrypted_inode(dir)) { + int res = ext4_get_encryption_info(dir); + + /* + * This should be a properly defined flag for + * dentry->d_flags when we uplift this to the VFS. + * d_fsdata is set to (void *) 1 if if the dentry is + * created while the directory was encrypted and we + * don't have access to the key. + */ + dentry->d_fsdata = NULL; + if (ext4_encryption_info(dir)) + dentry->d_fsdata = (void *) 1; + d_set_d_op(dentry, &ext4_encrypted_d_ops); + if (res && res != -ENOKEY) + return ERR_PTR(res); + } + if (dentry->d_name.len > EXT4_NAME_LEN) return ERR_PTR(-ENAMETOOLONG); Patches currently in stable-queue which might be from tytso@xxxxxxx are queue-4.4/ext4-fscrypto-avoid-rcu-lookup-in-d_revalidate.patch queue-4.4/ext4-crypto-revalidate-dentry-after-adding-or-removing-the-key.patch queue-4.4/ext4-crypto-use-dget_parent-in-ext4_d_revalidate.patch queue-4.4/ext4-require-encryption-feature-for-ext4_ioc_set_encryption_policy.patch