Re: [PATCH v1] nsproxy: Fix cred leak in the error path of prepare_nsset()

[Christian Brauner]

On Fri, 16 Oct 2026 23:35:38 -0400, Nickolai Zeldovich wrote:
> A task that calls setns() with CLONE_NEWUSER together with CLONE_NEWNS
> and at least one more namespace flag leaks a struct cred (and the
> user_namespace, ucounts and group_info references it holds) whenever the
> call fails at the fs_struct copy.  On a kernel with CONFIG_USER_NS the
> leak is one cred per failed setns(); under memory pressure, or driven by
> a fault-injecting attacker, it accumulates and pins user namespaces that
> can then never be freed.
> 
> [...]

Applied to the vfs.fixes branch of the vfs/vfs.git tree.
Patches in the vfs.fixes branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs.fixes

[1/1] nsproxy: Fix cred leak in the error path of prepare_nsset()
      https://git.kernel.org/vfs/vfs/c/486e02e391e6