ext3: Fix data / filesystem corruption when write fails to copy data
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@fuhm.net> Signed-off-by: Jan Kara <jack@suse.cz>
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@ -1151,6 +1151,16 @@ static int do_journal_get_write_access(handle_t *handle,
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return ext3_journal_get_write_access(handle, bh);
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}
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/*
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* Truncate blocks that were not used by write. We have to truncate the
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* pagecache as well so that corresponding buffers get properly unmapped.
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*/
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static void ext3_truncate_failed_write(struct inode *inode)
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{
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truncate_inode_pages(inode->i_mapping, inode->i_size);
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ext3_truncate(inode);
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}
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static int ext3_write_begin(struct file *file, struct address_space *mapping,
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loff_t pos, unsigned len, unsigned flags,
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struct page **pagep, void **fsdata)
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@ -1209,7 +1219,7 @@ write_begin_failed:
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unlock_page(page);
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page_cache_release(page);
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if (pos + len > inode->i_size)
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ext3_truncate(inode);
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ext3_truncate_failed_write(inode);
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}
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if (ret == -ENOSPC && ext3_should_retry_alloc(inode->i_sb, &retries))
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goto retry;
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@ -1304,7 +1314,7 @@ static int ext3_ordered_write_end(struct file *file,
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page_cache_release(page);
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if (pos + len > inode->i_size)
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ext3_truncate(inode);
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ext3_truncate_failed_write(inode);
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return ret ? ret : copied;
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}
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@ -1330,7 +1340,7 @@ static int ext3_writeback_write_end(struct file *file,
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page_cache_release(page);
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if (pos + len > inode->i_size)
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ext3_truncate(inode);
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ext3_truncate_failed_write(inode);
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return ret ? ret : copied;
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}
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@ -1383,7 +1393,7 @@ static int ext3_journalled_write_end(struct file *file,
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page_cache_release(page);
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if (pos + len > inode->i_size)
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ext3_truncate(inode);
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ext3_truncate_failed_write(inode);
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return ret ? ret : copied;
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}
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