Re: [PATCH 5/8] ipc: drop the mqueue mount with kern_unmount() on setup failure

[sashiko-bot@kernel.org]

> mq_init_ns() creates the mqueue mount with fc_mount_longterm(), so its
> ->mnt_ns is MNT_NS_INTERNAL. When setting up the mqueue or ipc sysctls
> or msg_init_ns() fails afterwards, create_ipc_ns() drops it with a plain
> mntput(). With ->mnt_ns set that takes the fast path of
> mntput_no_expire(). The count drops to zero and nothing ever kills the
> mount, so the mount and the mqueue superblock are leaked.
> 
> Commit dc55e35f9e81 ("ipc: Store mqueue sysctls in the ipc namespace")
> added the first failure path after mq_init_ns() and never dropped the
> mount. Commit 7229d74e5e8c ("ipc: create_ipc_ns: drop mqueue mount on
> sysctl setup failure") tried to fix that with a mntput() but that
> doesn't help for a long-term mount.
> 
> Use kern_unmount(). free_ipc() open-codes the same thing for a namespace
> that made it.
> 
> Fixes: dc55e35f9e81 ("ipc: Store mqueue sysctls in the ipc namespace")
> Fixes: 7229d74e5e8c ("ipc: create_ipc_ns: drop mqueue mount on sysctl setup failure")
> Cc: stable@vger.kernel.org
> Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20261009-work-fixes-rcu-v1-0-7446d2d335e6@kernel.org?part=5