From: Theodore Ts'o <tytso@xxxxxxx>
commit 28b4c263961c47da84ed8b5be0b5116bad1133eb upstream. Please apply
to 4.4-stable. [This fixes a bug where encrypted files cannot be opened
due to dcache pollution.]
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>
---
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(+)
diff --git a/fs/ext4/crypto.c b/fs/ext4/crypto.c
index 1a0835073663..13a69e0fb90d 100644
--- a/fs/ext4/crypto.c
+++ b/fs/ext4/crypto.c
@@ -469,3 +469,53 @@ uint32_t ext4_validate_encryption_key_size(uint32_t mode, uint32_t size)
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,
+};
diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
index 1d1bca74f844..6d17f31a31d7 100644
--- a/fs/ext4/dir.c
+++ b/fs/ext4/dir.c
@@ -111,6 +111,12 @@ static int ext4_readdir(struct file *file, struct dir_context *ctx)
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) {
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 362d59b24f1d..3de9bb357b4f 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2268,6 +2268,7 @@ struct page *ext4_encrypt(struct inode *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);
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 573b4cbb0cb9..fafa903ab3c0 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1557,6 +1557,24 @@ static struct dentry *ext4_lookup(struct inode *dir, struct dentry *dentry, unsi
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);
--
2.13.0.rc1.294.g07d810a77f-goog