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Miller" , dsahern@kernel.org, Greg Kroah-Hartman , Jakub Kicinski , liuhangbin@gmail.com, LKML , Linux MM Subject: Re: [PATCH] mm: mmap_lock: fix use-after-free race and css ref leak in tracepoints Message-ID: References: <20201130233504.3725241-1-axelrasmussen@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hello, On Wed, Dec 02, 2020 at 03:23:57PM -0800, Shakeel Butt wrote: > > There've been some changes to cgroup ids recently and now cgroup id, ino and > > its file_handle are all compatible. On 64bit ino machines, they're all the > > same and won't be reused. On 32bit ino machines, the lower 32bit of full id > > is used as ino. ino may be reused but not the full 64bit id. > > __kernfs_new_node() is using idr_alloc_cyclic() which will return > 32bit ID. If I am understanding this correctly the full ID is > generated similarly for 32bit and 64bit machines but for 64bit > machines the whole ID is inode number while on 32bit machines the > lower 32bits contains the inode number. Is that correct? Yes, that's correct. Thanks. -- tejun