** Description changed: + [Impact] + + * Any attempt to create/overwrite symlinks in a partition mounted by + fuseext2 causes the fuseext2 process to deadlock, preventing the mounted + filesystem from being used at all until the userspace process is killed + and the filesystem is remounted. + + [Test Case] + + * dd if=/dev/zero of=partition bs=1M count=200 + * mkfs.ext2 partition + * mkdir mount + * fuseext2 partition mount + * cd mount + * touch test + * ln -s test link - Doesn't complete + * In another shell try to do anything else in the mount directory (ls, touch, rm) - Don't complete + + [Regression Potential] + + * Since this changes the locking strategy of the code to hold locks less, the main risk is exposing a case where data can be accessed in a non-threadsafe manner, leading to unexpected behaviour. + * The places where the change has been made are at the exit points of the function, and match where similar unlocks are made in other places in the code. + * Since the program at risk is (by design) a userspace program, the risk of kernel data leakage is minimal. + + [Other Info] + + * I can't actually work out where the upstream code for this project lives, the only upstream I could find is https://github.com/alperakcan/fuse-ext2 but that doesn't have any locking code at all (even in the reentrant branch) so I can't see where this issue came from. + * This issue seems to apply to all versions of fuseext2 in the ubuntu repos (well, at least it's there in trusty, xenial and zesty) + + [Original Description] + Trying to create a symlink in a filesystem mounted by fuseext2 causes the fuseext2 userspace process to deadlock before responding to the fuse request. This is simply due to a code bug in fuse-ext2/op_link.c (lines 104 and 109) where the code calls FUSE_EXT2_LOCK rather than FUSE_EXT2_UNLOCK on exiting the function. I've confirmed that making that changes allows me to create symlinks happily on the mounted filesystem. The bug appears to exist upstream too. System info: $ lsb_release -rd Description: Linux Mint 18.1 Serena Release: 18.1 Software version: $ apt show fuseext2 Package: fuseext2 Version: 0.4-1.1 Priority: optional Section: universe/misc Source: fuse-umfuse-ext2 Origin: Ubuntu Maintainer: Ubuntu Developers <ubuntu-devel-disc...@lists.ubuntu.com> Original-Maintainer: Debian VSquare Team <pkg-vsquare-de...@lists.alioth.debian.org> Bugs: https://bugs.launchpad.net/ubuntu/+filebug Installed-Size: 103 kB Depends: e2fslibs (>= 1.42), libc6 (>= 2.4), libfuse2 (>= 2.8.1), fuse Homepage: http://view-os.sourceforge.net Download-Size: 24.7 kB APT-Manual-Installed: yes APT-Sources: http://archive.ubuntu.com/ubuntu xenial/universe amd64 Packages
** Also affects: fuse-umfuse-ext2 (Ubuntu Trusty) Importance: Undecided Status: New ** Changed in: fuse-umfuse-ext2 (Ubuntu) Status: New => Fix Released ** Changed in: fuse-umfuse-ext2 (Ubuntu Trusty) Importance: Undecided => High ** Changed in: fuse-umfuse-ext2 (Ubuntu Trusty) Status: New => Confirmed -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1674868 Title: Fuse-ext2 deadlocks on creating symlinks To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/fuse-umfuse-ext2/+bug/1674868/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs