fs/ntfs3: resize log->one_page_buf when adopting on-disk page size

Summary

In the Linux kernel, the following vulnerability has been resolved: fs/ntfs3: resize log->one_page_buf when adopting on-disk page size log_replay() allocates log->one_page_buf using the page size that was chosen from the host PAGE_SIZE: log->one_page_buf = kmalloc(log->page_size, GFP_NOFS); Later, when a restart area is found, the log page size recorded on disk is adopted: t32 = le32_to_cpu(log->rst_info.r_page->sys_page_size); if (log->page_size != t32) { log->l_size = log->orig_file_size; log->page_size = norm_file_page(t32, &log->l_size, t32 == DefaultLogPageSize); } If the on-disk page size is larger than the size used for the initial allocation, log->page_size grows but one_page_buf is left at its original, smaller size. A subsequent unaligned read_log_page() then reads log->page_size bytes into the undersized scratch buffer: page_buf = page_off ? log->one_page_buf : *buffer; err = ntfs_read_run_nb_ra(ni->mi.sbi, &ni->file.run, page_vbo, page_buf, log->page_size, NULL, &log->read_ahead); overflowing the allocation. This is reachable when mounting a dirty NTFS volume whose log was formatted with a page size larger than the buffer initially allocated on the mounting host (for example a 64K-log volume mounted on a host that allocated a 4K scratch buffer). Grow one_page_buf when the adopted on-disk page size exceeds the size used for the initial allocation. On krealloc() failure the original buffer is left intact and freed by the existing error path.