eCryptfs: Do not allocate hash tfm in NORECLAIM context

herbertx · herbertx · commit e81f3340bba2 · 2016-04-20T17:50:01.000+08:00
You cannot allocate crypto tfm objects in NORECLAIM or NOFS contexts.
The ecryptfs code currently does exactly that for the MD5 tfm.

This patch fixes it by preallocating the MD5 tfm in a safe context.

The MD5 tfm is also reentrant so this patch removes the superfluous
cs_hash_tfm_mutex.

Reported-by: Nicolas Boichat &lt;drinkcat@chromium.org&gt;
Signed-off-by: Herbert Xu &lt;herbert@gondor.apana.org.au&gt;
diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
@@ -105,19 +105,7 @@ static int ecryptfs_calculate_md5(char *dst,
 	struct crypto_shash *tfm;
 	int rc = 0;
 
-	mutex_lock(&crypt_stat->cs_hash_tfm_mutex);
 	tfm = crypt_stat->hash_tfm;
-	if (!tfm) {
-		tfm = crypto_alloc_shash(ECRYPTFS_DEFAULT_HASH, 0, 0);
-		if (IS_ERR(tfm)) {
-			rc = PTR_ERR(tfm);
-			ecryptfs_printk(KERN_ERR, "Error attempting to "
-					"allocate crypto context; rc = [%d]\n",
-					rc);
-			goto out;
-		}
-		crypt_stat->hash_tfm = tfm;
-	}
 	rc = ecryptfs_hash_digest(tfm, src, len, dst);
 	if (rc) {
 		printk(KERN_ERR
@@ -126,7 +114,6 @@ static int ecryptfs_calculate_md5(char *dst,
 		goto out;
 	}
 out:
-	mutex_unlock(&crypt_stat->cs_hash_tfm_mutex);
 	return rc;
 }
 
@@ -207,16 +194,29 @@ int ecryptfs_derive_iv(char *iv, struct ecryptfs_crypt_stat *crypt_stat,
  *
  * Initialize the crypt_stat structure.
  */
-void
-ecryptfs_init_crypt_stat(struct ecryptfs_crypt_stat *crypt_stat)
+int ecryptfs_init_crypt_stat(struct ecryptfs_crypt_stat *crypt_stat)
 {
+	struct crypto_shash *tfm;
+	int rc;
+
+	tfm = crypto_alloc_shash(ECRYPTFS_DEFAULT_HASH, 0, 0);
+	if (IS_ERR(tfm)) {
+		rc = PTR_ERR(tfm);
+		ecryptfs_printk(KERN_ERR, "Error attempting to "
+				"allocate crypto context; rc = [%d]\n",
+				rc);
+		return rc;
+	}
+
 	memset((void *)crypt_stat, 0, sizeof(struct ecryptfs_crypt_stat));
 	INIT_LIST_HEAD(&crypt_stat->keysig_list);
 	mutex_init(&crypt_stat->keysig_list_mutex);
 	mutex_init(&crypt_stat->cs_mutex);
 	mutex_init(&crypt_stat->cs_tfm_mutex);
-	mutex_init(&crypt_stat->cs_hash_tfm_mutex);
+	crypt_stat->hash_tfm = tfm;
 	crypt_stat->flags |= ECRYPTFS_STRUCT_INITIALIZED;
+
+	return 0;
 }
 
 /**
diff --git a/fs/ecryptfs/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h
@@ -242,7 +242,6 @@ struct ecryptfs_crypt_stat {
 	struct list_head keysig_list;
 	struct mutex keysig_list_mutex;
 	struct mutex cs_tfm_mutex;
-	struct mutex cs_hash_tfm_mutex;
 	struct mutex cs_mutex;
 };
 
@@ -577,7 +576,7 @@ int virt_to_scatterlist(const void *addr, int size, struct scatterlist *sg,
 			int sg_size);
 int ecryptfs_compute_root_iv(struct ecryptfs_crypt_stat *crypt_stat);
 void ecryptfs_rotate_iv(unsigned char *iv);
-void ecryptfs_init_crypt_stat(struct ecryptfs_crypt_stat *crypt_stat);
+int ecryptfs_init_crypt_stat(struct ecryptfs_crypt_stat *crypt_stat);
 void ecryptfs_destroy_crypt_stat(struct ecryptfs_crypt_stat *crypt_stat);
 void ecryptfs_destroy_mount_crypt_stat(
 	struct ecryptfs_mount_crypt_stat *mount_crypt_stat);
diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
@@ -898,8 +898,11 @@ static int ecryptfs_setattr(struct dentry *dentry, struct iattr *ia)
 	struct ecryptfs_crypt_stat *crypt_stat;
 
 	crypt_stat = &ecryptfs_inode_to_private(d_inode(dentry))->crypt_stat;
-	if (!(crypt_stat->flags & ECRYPTFS_STRUCT_INITIALIZED))
-		ecryptfs_init_crypt_stat(crypt_stat);
+	if (!(crypt_stat->flags & ECRYPTFS_STRUCT_INITIALIZED)) {
+		rc = ecryptfs_init_crypt_stat(crypt_stat);
+		if (rc)
+			return rc;
+	}
 	inode = d_inode(dentry);
 	lower_inode = ecryptfs_inode_to_lower(inode);
 	lower_dentry = ecryptfs_dentry_to_lower(dentry);
diff --git a/fs/ecryptfs/super.c b/fs/ecryptfs/super.c
@@ -55,7 +55,10 @@ static struct inode *ecryptfs_alloc_inode(struct super_block *sb)
 	inode_info = kmem_cache_alloc(ecryptfs_inode_info_cache, GFP_KERNEL);
 	if (unlikely(!inode_info))
 		goto out;
-	ecryptfs_init_crypt_stat(&inode_info->crypt_stat);
+	if (ecryptfs_init_crypt_stat(&inode_info->crypt_stat)) {
+		kmem_cache_free(ecryptfs_inode_info_cache, inode_info);
+		goto out;
+	}
 	mutex_init(&inode_info->lower_file_mutex);
 	atomic_set(&inode_info->lower_file_count, 0);
 	inode_info->lower_file = NULL;
