udf: Fix deadlock when converting file from in-ICB one to normal one

During BKL removal in 2.6.38, conversion of files from in-ICB format to normal
format got broken. We call ->writepage with i_data_sem held but udf_get_block()
also acquires i_data_sem thus creating A-A deadlock.

We fix the problem by dropping i_data_sem before calling ->writepage() which is
safe since i_mutex still protects us against any changes in the file. Also fix
pagelock - i_data_sem lock inversion in udf_expand_file_adinicb() by dropping
i_data_sem before calling find_or_create_page().

CC: stable@kernel.org
Reported-by: Matthias Matiak <netzpython@mail-on.us>
Tested-by: Matthias Matiak <netzpython@mail-on.us>
Reviewed-by: Namjae Jeon <linkinjeon@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 18 insertions, 3 deletions

diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 1bd2c42f3b48..4f7b1ffd9e37 100644
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -150,6 +150,12 @@ const struct address_space_operations udf_aops = {
         .bmap           = udf_bmap,
 };
 
+/*
+ * Expand file stored in ICB to a normal one-block-file
+ *
+ * This function requires i_data_sem for writing and releases it.
+ * This function requires i_mutex held
+ */
 int udf_expand_file_adinicb(struct inode *inode)
 {
         struct page *page;
@@ -168,9 +174,15 @@ int udf_expand_file_adinicb(struct inode *inode)
                         iinfo->i_alloc_type = ICBTAG_FLAG_AD_LONG;
                 /* from now on we have normal address_space methods */
                 inode->i_data.a_ops = &udf_aops;
+                up_write(&iinfo->i_data_sem);
                 mark_inode_dirty(inode);
                 return 0;
         }
+        /*
+         * Release i_data_sem so that we can lock a page - page lock ranks
+         * above i_data_sem. i_mutex still protects us against file changes.
+         */
+        up_write(&iinfo->i_data_sem);
 
         page = find_or_create_page(inode->i_mapping, 0, GFP_NOFS);
         if (!page)
@@ -186,6 +198,7 @@ int udf_expand_file_adinicb(struct inode *inode)
                 SetPageUptodate(page);
                 kunmap(page);
         }
+        down_write(&iinfo->i_data_sem);
         memset(iinfo->i_ext.i_data + iinfo->i_lenEAttr, 0x00,
                iinfo->i_lenAlloc);
         iinfo->i_lenAlloc = 0;
@@ -195,17 +208,20 @@ int udf_expand_file_adinicb(struct inode *inode)
                 iinfo->i_alloc_type = ICBTAG_FLAG_AD_LONG;
         /* from now on we have normal address_space methods */
         inode->i_data.a_ops = &udf_aops;
+        up_write(&iinfo->i_data_sem);
         err = inode->i_data.a_ops->writepage(page, &udf_wbc);
         if (err) {
                 /* Restore everything back so that we don't lose data... */
                 lock_page(page);
                 kaddr = kmap(page);
+                down_write(&iinfo->i_data_sem);
                 memcpy(iinfo->i_ext.i_data + iinfo->i_lenEAttr, kaddr,
                        inode->i_size);
                 kunmap(page);
                 unlock_page(page);
                 iinfo->i_alloc_type = ICBTAG_FLAG_AD_IN_ICB;
                 inode->i_data.a_ops = &udf_adinicb_aops;
+                up_write(&iinfo->i_data_sem);
         }
         page_cache_release(page);
         mark_inode_dirty(inode);
@@ -1105,10 +1121,9 @@ int udf_setsize(struct inode *inode, loff_t newsize)
                         if (bsize <
                             (udf_file_entry_alloc_offset(inode) + newsize)) {
                                 err = udf_expand_file_adinicb(inode);
-                                if (err) {
-                                        up_write(&iinfo->i_data_sem);
+                                if (err)
                                         return err;
-                                }
+                                down_write(&iinfo->i_data_sem);
                         } else
                                 iinfo->i_lenAlloc = newsize;
                 }