[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) -- 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
