vfs: Don't call attach_nobh_buffers() with an empty list This is a modification of a patch by Bill Pemberton <wfp5p@xxxxxxxxxxxx> nobh_write_end() could call attach_nobh_buffers() with head == NULL. This would result in a trap when attach_nobh_buffers() attempted to access bh->b_this_page. This can be illustrated by running the writev01 testcase from LTP on jfs. This error was introduced by commit 5b41e74a "vfs: fix data leak in nobh_write_end()". That patch did not take into account that if PageMappedToDisk() is true upon entry to nobh_write_begin(), then no buffers will be allocated for the page. In that case, we won't have to worry about a failed write leaving unitialized data in the page. Of course, head != NULL implies !page_has_buffers(page), so no need to test both. Signed-off-by: Dave Kleikamp <shaggy@xxxxxxxxxxxxxxxxxx> Cc: Bill Pemberton <wfp5p@xxxxxxxxxxxx> Cc: Dmitri Monakhov <dmonakhov@xxxxxxxxxx> diff --git a/fs/buffer.c b/fs/buffer.c index b58208f..665d446 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -2688,7 +2688,7 @@ int nobh_write_end(struct file *file, struct address_space *mapping, struct buffer_head *bh; BUG_ON(fsdata != NULL && page_has_buffers(page)); - if (unlikely(copied < len) && !page_has_buffers(page)) + if (unlikely(copied < len) && head) attach_nobh_buffers(page, head); if (page_has_buffers(page)) return generic_write_end(file, mapping, pos, len, -- David Kleikamp IBM Linux Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
