[PATCH] eCryptfs: Reduce stack usage in ecryptfs_generate_key_packet_set()

eCryptfs is gobbling a lot of stack in ecryptfs_generate_key_packet_set()
because it allocates a temporary memory-hungry ecryptfs_key_record struct.
This patch introduces a new kmem_cache for that struct and converts
ecryptfs_generate_key_packet_set() to use it.

Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 24 insertions, 8 deletions

diff --git a/fs/ecryptfs/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h
index b3609b7cdf11..403e3bad1455 100644
--- a/fs/ecryptfs/ecryptfs_kernel.h
+++ b/fs/ecryptfs/ecryptfs_kernel.h
@@ -467,6 +467,7 @@ extern struct kmem_cache *ecryptfs_header_cache_1;
 extern struct kmem_cache *ecryptfs_header_cache_2;
 extern struct kmem_cache *ecryptfs_xattr_cache;
 extern struct kmem_cache *ecryptfs_lower_page_cache;
+extern struct kmem_cache *ecryptfs_key_record_cache;
 
 int ecryptfs_interpose(struct dentry *hidden_dentry,
                        struct dentry *this_dentry, struct super_block *sb,
diff --git a/fs/ecryptfs/keystore.c b/fs/ecryptfs/keystore.c
index 81156e95ef8e..b550dea8eee6 100644
--- a/fs/ecryptfs/keystore.c
+++ b/fs/ecryptfs/keystore.c
@@ -1638,6 +1638,8 @@ out:
         return rc;
 }
 
+struct kmem_cache *ecryptfs_key_record_cache;
+
 /**
  * ecryptfs_generate_key_packet_set
  * @dest: Virtual address from which to write the key record set
@@ -1664,50 +1666,55 @@ ecryptfs_generate_key_packet_set(char *dest_base,
                 &ecryptfs_superblock_to_private(
                         ecryptfs_dentry->d_sb)->mount_crypt_stat;
         size_t written;
-        struct ecryptfs_key_record key_rec;
+        struct ecryptfs_key_record *key_rec;
         int rc = 0;
 
         (*len) = 0;
+        key_rec = kmem_cache_alloc(ecryptfs_key_record_cache, GFP_KERNEL);
+        if (!key_rec) {
+                rc = -ENOMEM;
+                goto out;
+        }
         if (mount_crypt_stat->global_auth_tok) {
                 auth_tok = mount_crypt_stat->global_auth_tok;
                 if (auth_tok->token_type == ECRYPTFS_PASSWORD) {
                         rc = write_tag_3_packet((dest_base + (*len)),
                                                 max, auth_tok,
-                                                crypt_stat, &key_rec,
+                                                crypt_stat, key_rec,
                                                 &written);
                         if (rc) {
                                 ecryptfs_printk(KERN_WARNING, "Error "
                                                 "writing tag 3 packet\n");
-                                goto out;
+                                goto out_free;
                         }
                         (*len) += written;
                         /* Write auth tok signature packet */
                         rc = write_tag_11_packet(
                                 (dest_base + (*len)),
                                 (max - (*len)),
-                                key_rec.sig, ECRYPTFS_SIG_SIZE, &written);
+                                key_rec->sig, ECRYPTFS_SIG_SIZE, &written);
                         if (rc) {
                                 ecryptfs_printk(KERN_ERR, "Error writing "
                                                 "auth tok signature packet\n");
-                                goto out;
+                                goto out_free;
                         }
                         (*len) += written;
                 } else if (auth_tok->token_type == ECRYPTFS_PRIVATE_KEY) {
                         rc = write_tag_1_packet(dest_base + (*len),
                                                 max, auth_tok,
                                                 crypt_stat,mount_crypt_stat,
-                                                &key_rec, &written);
+                                                key_rec, &written);
                         if (rc) {
                                 ecryptfs_printk(KERN_WARNING, "Error "
                                                 "writing tag 1 packet\n");
-                                goto out;
+                                goto out_free;
                         }
                         (*len) += written;
                 } else {
                         ecryptfs_printk(KERN_WARNING, "Unsupported "
                                         "authentication token type\n");
                         rc = -EINVAL;
-                        goto out;
+                        goto out_free;
                 }
         } else
                 BUG();
@@ -1717,6 +1724,9 @@ ecryptfs_generate_key_packet_set(char *dest_base,
                 ecryptfs_printk(KERN_ERR, "Error writing boundary byte\n");
                 rc = -EIO;
         }
+
+out_free:
+        kmem_cache_free(ecryptfs_key_record_cache, key_rec);
 out:
         if (rc)
                 (*len) = 0;
diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c
index 26fe405a5763..80044d196fe0 100644
--- a/fs/ecryptfs/main.c
+++ b/fs/ecryptfs/main.c
@@ -651,6 +651,11 @@ static struct ecryptfs_cache_info {
                 .name = "ecryptfs_lower_page_cache",
                 .size = PAGE_CACHE_SIZE,
         },
+        {
+                .cache = &ecryptfs_key_record_cache,
+                .name = "ecryptfs_key_record_cache",
+                .size = sizeof(struct ecryptfs_key_record),
+        },
 };
 
 static void ecryptfs_free_kmem_caches(void)