When ext3_write_begin fails after allocating some blocks or
generic_perform_write fails to copy data to write, we truncate blocks already
instantiated beyond i_size. Although these blocks were never inside i_size, we
have to truncate pagecache of these blocks so that corresponding buffers get
unmapped. Otherwise subsequent __block_prepare_write (called because we are
retrying the write) will find the buffers mapped, not call ->get_block, and
thus the page will be backed by already freed blocks leading to filesystem and
data corruption.
Reported-by: James Y Knight <foom@xxxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
fs/ext3/inode.c | 18 ++++++++++++++----
1 files changed, 14 insertions(+), 4 deletions(-)
The bug has been introduced by commit 9eaaa2d5759837402ec5eee13b2a97921808c3eb
and thus this fix needs to be applied to 2.6.31 and 2.6.32 kernels. Currently,
it's in Linus's tree as commit 68eb3db08344286733adac48304d9fb7a0e53b27.
diff --git a/fs/ext3/inode.c b/fs/ext3/inode.c
index 354ed3b..f9d6937 100644
--- a/fs/ext3/inode.c
+++ b/fs/ext3/inode.c
@@ -1151,6 +1151,16 @@ static int do_journal_get_write_access(handle_t *handle,
return ext3_journal_get_write_access(handle, bh);
}
+/*
+ * Truncate blocks that were not used by write. We have to truncate the
+ * pagecache as well so that corresponding buffers get properly unmapped.
+ */
+static void ext3_truncate_failed_write(struct inode *inode)
+{
+ truncate_inode_pages(inode->i_mapping, inode->i_size);
+ ext3_truncate(inode);
+}
+
static int ext3_write_begin(struct file *file, struct address_space *mapping,
loff_t pos, unsigned len, unsigned flags,
struct page **pagep, void **fsdata)
@@ -1209,7 +1219,7 @@ write_begin_failed:
unlock_page(page);
page_cache_release(page);
if (pos + len > inode->i_size)
- ext3_truncate(inode);
+ ext3_truncate_failed_write(inode);
}
if (ret == -ENOSPC && ext3_should_retry_alloc(inode->i_sb, &retries))
goto retry;
@@ -1304,7 +1314,7 @@ static int ext3_ordered_write_end(struct file *file,
page_cache_release(page);
if (pos + len > inode->i_size)
- ext3_truncate(inode);
+ ext3_truncate_failed_write(inode);
return ret ? ret : copied;
}
@@ -1330,7 +1340,7 @@ static int ext3_writeback_write_end(struct file *file,
page_cache_release(page);
if (pos + len > inode->i_size)
- ext3_truncate(inode);
+ ext3_truncate_failed_write(inode);
return ret ? ret : copied;
}
@@ -1383,7 +1393,7 @@ static int ext3_journalled_write_end(struct file *file,
page_cache_release(page);
if (pos + len > inode->i_size)
- ext3_truncate(inode);
+ ext3_truncate_failed_write(inode);
return ret ? ret : copied;
}
--
1.6.4.2
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