Merge tag 'v7.2' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux into gpio/for-next

Linux 7.2

Merge tag 'vfs-7.2-rc8.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull vfs fixes from Christian Brauner:

- Don't warn when a mount is completed from another user namespace.

Merge tag 'vfs-7.2-rc8.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull vfs fixes from Christian Brauner:

- Don't warn when a mount is completed from another user namespace.

fsopen() records the caller's user namespace in fc->user_ns and
hands back an ordinary file descriptor. The task that calls
fsconfig(FSCONFIG_CMD_CREATE) doesn't have to be the one that
created the context, and mount_capable() lets it through as long
as the caller has CAP_SYS_ADMIN over fc->user_ns, which anyone in
an ancestor namespace does. So fc->user_ns != current_user_ns()
is something an unprivileged user can arrange.

Both overlayfs and binfmt_misc WARN_ON() that. Overlayfs already
has the same check as a plain error return in ovl_parse_param().

Drop the WARN_ON() and just refuse. Add selftests for both cases.

- Reject pid allocations through dead ancestor pid namespaces.

Require PIDNS_ADDING in every namespace that will receive the pid
before publishing any of them. That preserves the invariant that
free_pid() never decrements pid_allocated in a namespace whose
child_reaper is no longer live. The existing ENOMEM behavior is
unchanged.

* tag 'vfs-7.2-rc8.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
pid: reject allocations through dead ancestor pid namespaces
selftests/filesystems: test completing a context from another user namespace
binfmt_misc: don't warn when the mount is completed from another user namespace
ovl: don't warn when the mount is completed from another user namespace

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Merge patch series "fs: don't warn when a mount is completed from another user namespace"

Christian Brauner <brauner@kernel.org> says:

fsopen() records the caller's user namespace in fc->user_ns an

Merge patch series "fs: don't warn when a mount is completed from another user namespace"

Christian Brauner <brauner@kernel.org> says:

fsopen() records the caller's user namespace in fc->user_ns and hands back
an ordinary file descriptor. The task that calls fsconfig(CMD_CREATE)
doesn't have to be the one that created the context, and mount_capable()
lets it through as long as the caller has CAP_SYS_ADMIN over fc->user_ns,
which anyone in an ancestor namespace does. So fc->user_ns !=
current_user_ns() is something an unprivileged user can arrange.

Both overlayfs and binfmt_misc WARN_ON() that. They're plain WARN_ON()s, so
it can be done in a loop to taint the kernel and flood the log, and it
panics a machine booted with panic_on_warn. Keep refusing the mount, just
stop warning about it. Overlayfs already spells the same check as a plain
error return in ovl_parse_param() for Opt_override_creds.

And add a selftest for both cases.

* patches from https://patch.msgid.link/20260802-work-fill_super-warn-v1-0-4e987911a39a@kernel.org:
selftests/filesystems: test completing a context from another user namespace
binfmt_misc: don't warn when the mount is completed from another user namespace
ovl: don't warn when the mount is completed from another user namespace

Link: https://patch.msgid.link/20260802-work-fill_super-warn-v1-0-4e987911a39a@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

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selftests/filesystems: test completing a context from another user namespace

fsopen() records the caller's user namespace in fc->user_ns and hands
back an ordinary file descriptor, so the task that

selftests/filesystems: test completing a context from another user namespace

fsopen() records the caller's user namespace in fc->user_ns and hands
back an ordinary file descriptor, so the task that issues
FSCONFIG_CMD_CREATE need not be the one that created the context.
mount_capable() authorizes that for a caller holding CAP_SYS_ADMIN in an
ancestor of fc->user_ns, which any unprivileged user has over a user
namespace it just created.

binfmt_misc and overlayfs used to WARN_ON() the mismatch. Add a test for
both. Also cover the handover within one user namespace. That is a
supported thing to do and has to keep working.

Link: https://patch.msgid.link/20260802-work-fill_super-warn-v1-3-4e987911a39a@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

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