On Mon, Sep 02, 2013 at 05:53:42PM +0100, Simon Farnsworth wrote: > On Monday 2 September 2013 18:43:58 David Sterba wrote: > > Yes that's what I meant and that's what dupremove in your git tree does, > > right? > > > > Using the EXTENT_SAME ioctl without any checks is dangerous, and that's > > what btrfs-extent-same.c does, so it's suitable for testing but not > > about to be given to users as-is. > > > Why is using EXTENT_SAME without any checks dangerous? > > If userspace has to do checks to guarantee safety, what stops an attacker > deliberately triggering a TOCTTOU race against a checked user of EXTENT_SAME? > I would expect that unchecked use of EXTENT_SAME simply causes the kernel to > return BTRFS_SAME_DATA_DIFFERS most of the time, thus slowing you down. I was mistaken, the ioctl does checks before merging the extents. Sorry for confusion. david -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
