** Description changed: - To be filled in... + Under some conditions, after fallocate() the file is observed not to be + completely initilized to 0s: some 4KB pages have left-over data from + previous files that occupied those pages. Note that in addition to + causing functional problems for applications expecting files to be + initialized to 0s, this is a security issue because it allows data to + "leak" from one file to another, bypassing file access controls. + + The problem has been seen running under the following VMWare-based virtual environments: + Fusion 6.0.2 + ESXi 5.1.0 + + And under the following versions of Ubuntu: + Ubuntu 12.04, 3.11.0-26-generic + Ubuntu 14.04.1, 3.13.0-32-generic + Ubuntu 14.04.1, 3.13.0-35-generic + + But did not reproduce under the following version: + Ubuntu 10.04, 2.6.32-38-server + + The problem reproduced under LVM, but did not reproduce without LVM. + + I reproduced the problem as follows under VMWare Fusion: + set up custom VM with default disk size (20 GB) and memory size (1 GB) + attach Ubuntu 14.04.1 ISO to CDROM, set it as boot device, boot up + select all defaults during installation _except_ LVM + install gcc + unpack the attached repro.tgz + run repro.sh + + what it does: + * fills the disk with a file containing bytes of 0xcc then deletes it + * repeatedly runs the repro program which creates two files and accesses them in a certain pattern + * checks the file f0 with hexdump; it should contain all 0s, but if pages 0x1000-0x7000 contain 0xcc you have reproduced the problem + + If the problem does not appear to reproduce, please try waiting a bit + and checking the f0 files with hexdump again. This behavior was observed + by a customer reproducing the problem under ESXi. I since added an sync + after the running the repro binary which I think will fix that. + + If you still can't reproduce the problem please let me know if there's + anything I can do to help. For example can we trace the disk accesses at + the SCSI level to verify whether the appropriate SCSI commands are being + sent? This may help determine whether the problem is in Linux or in + VMWare.
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1371591 Title: file not initialized to 0s under some conditions on VMWare To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1371591/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
