[PATCH] eCryptfs: resolve lower page unlocking problem

eCryptfs lower file handling code has several issues:
  - Retval from prepare_write()/commit_write() wasn't checked to equality
    to AOP_TRUNCATED_PAGE.
  - In some places page wasn't unmapped and unlocked after error.

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>

1 files changed, 23 insertions, 5 deletions

diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c
index 3a6f65c3f14f..82bdbed658d7 100644
--- a/fs/ecryptfs/mmap.c
+++ b/fs/ecryptfs/mmap.c
@@ -422,9 +422,11 @@ out:
         return rc;
 }
 
-static void ecryptfs_release_lower_page(struct page *lower_page)
+static
+void ecryptfs_release_lower_page(struct page *lower_page, int page_locked)
 {
-        unlock_page(lower_page);
+        if (page_locked)
+                unlock_page(lower_page);
         page_cache_release(lower_page);
 }
 
@@ -454,6 +456,13 @@ static int ecryptfs_write_inode_size_to_header(struct file *lower_file,
         }
         lower_a_ops = lower_inode->i_mapping->a_ops;
         rc = lower_a_ops->prepare_write(lower_file, header_page, 0, 8);
+        if (rc) {
+                if (rc == AOP_TRUNCATED_PAGE)
+                        ecryptfs_release_lower_page(header_page, 0);
+                else
+                        ecryptfs_release_lower_page(header_page, 1);
+                goto out;
+        }
         file_size = (u64)i_size_read(inode);
         ecryptfs_printk(KERN_DEBUG, "Writing size: [0x%.16x]\n", file_size);
         file_size = cpu_to_be64(file_size);
@@ -465,7 +474,10 @@ static int ecryptfs_write_inode_size_to_header(struct file *lower_file,
         if (rc < 0)
                 ecryptfs_printk(KERN_ERR, "Error commiting header page "
                                 "write\n");
-        ecryptfs_release_lower_page(header_page);
+        if (rc == AOP_TRUNCATED_PAGE)
+                ecryptfs_release_lower_page(header_page, 0);
+        else
+                ecryptfs_release_lower_page(header_page, 1);
         lower_inode->i_mtime = lower_inode->i_ctime = CURRENT_TIME;
         mark_inode_dirty_sync(inode);
 out:
@@ -572,7 +584,10 @@ int ecryptfs_get_lower_page(struct page **lower_page, struct inode *lower_inode,
         }
 out:
         if (rc && (*lower_page)) {
-                ecryptfs_release_lower_page(*lower_page);
+                if (rc == AOP_TRUNCATED_PAGE)
+                        ecryptfs_release_lower_page(*lower_page, 0);
+                else
+                        ecryptfs_release_lower_page(*lower_page, 1);
                 (*lower_page) = NULL;
         }
         return rc;
@@ -588,16 +603,19 @@ ecryptfs_commit_lower_page(struct page *lower_page, struct inode *lower_inode,
                            struct file *lower_file, int byte_offset,
                            int region_size)
 {
+        int page_locked = 1;
         int rc = 0;
 
         rc = lower_inode->i_mapping->a_ops->commit_write(
                 lower_file, lower_page, byte_offset, region_size);
+        if (rc == AOP_TRUNCATED_PAGE)
+                page_locked = 0;
         if (rc < 0) {
                 ecryptfs_printk(KERN_ERR,
                                 "Error committing write; rc = [%d]\n", rc);
         } else
                 rc = 0;
-        ecryptfs_release_lower_page(lower_page);
+        ecryptfs_release_lower_page(lower_page, page_locked);
         return rc;
 }