Linux Kernel IPC mqueue mount leak due to improper unmount
CVE-2026-99172 Published on October 28, 2026
ipc: drop the mqueue mount with kern_unmount() on setup failure
In the Linux kernel, the following vulnerability has been resolved:
ipc: drop the mqueue mount with kern_unmount() on setup failure
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.
Products Associated with CVE-2026-99172
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Affected Versions
Linux:- Version dc55e35f9e810f23dd69cfdc91a3d636023f57a2 and below c0620b648321fff654173d238d4a85298ea16d05 is affected.
- Version dc55e35f9e810f23dd69cfdc91a3d636023f57a2 and below f0e48172a59e517e613b73f73cc35f24fd123aeb is affected.
- Version 5.19 is affected.
- Before 5.19 is unaffected.
- Version 7.2.13, <= 7.2.* is unaffected.
- Version 7.3, <= * is unaffected.