On Fri, Feb 28, 2014 at 08:14:45PM -0500, Sasha Levin wrote: > Hi all, > > I've stumbled on the following while fuzzing with trinity inside a > KVM tools running the latest -next kernel. > > We deal with files that have an mmap op by giving them a different > locking class than the files which don't due to mmap_sem nesting > being different for those files. > > We assume that for mmap supporting files, of->mutex will be nested > inside mm->mmap_sem. However, this is not always the case. Consider > the following: > > kernfs_fop_write() > copy_from_user() > might_fault() > > might_fault() suggests that we may lock mm->mmap_sem, which causes a > reverse lock nesting of mm->mmap_sem inside of of->mutex. > > I'll send a patch to fix it some time next week unless someone beats me to it > :)
How are you planning to fix it? Prolly the right thing to do would be caching atomic_write_len in open_file and copy data before grabbing any locks. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
