On Wed, Sep 20, 2017 at 04:08:24PM -0700, Darrick J. Wong wrote: > > I'm still wondering why we allocate a potentially large getbmapx buffer, > > fill it out, and only then format the results to userspace? I think > > getbmap (the ioctl) is now the only user of these functions, so can't > > we just call the formatter directly from _getbmap_report_one and > > _getbmap_report_hole, like what getfsmap does? > > > > (I also feel like I've asked this before, so apologies if I'm merely > > forgetting the answer.) > > Oh right, it's because we have the inode locked, and copying things to > userspace could incur a page fault, which we can't risk with the inode > locked because some malicious person could create a fragmented file with > a bmap request header at the start of the file, mmap the file, and call > bmap on the fragmented file with the pointer being the mmap region. Yes. Can I get a Reviewed-by: tag now? :) -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
