From: ebiederm@xmission.com (Eric W. Biederman)
To: David Howells <dhowells@redhat.com>
Cc: Alan Jenkins <alan.christopher.jenkins@gmail.com>,
viro@zeniv.linux.org.uk, torvalds@linux-foundation.org,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
mszeredi@redhat.com
Subject: Re: [PATCH 03/34] teach move_mount(2) to work with OPEN_TREE_CLONE [ver #12]
Date: Thu, 11 Oct 2018 13:38:31 -0500 [thread overview]
Message-ID: <87sh1cqqfs.fsf@xmission.com> (raw)
In-Reply-To: <17405.1539272035@warthog.procyon.org.uk> (David Howells's message of "Thu, 11 Oct 2018 16:33:55 +0100")
David Howells <dhowells@redhat.com> writes:
> Okay, this appears to fix the cycle-creation problem.
>
> It could probably be improved by comparing sequence numbers as Alan suggests,
> but I need to work out how to get at that.
It should just be a matter of replacing the test
"if (p->mnt.mnt_sb->s_type == &nsfs)" with "if mnt_ns_loop(p->mnt.mnt_root)"
That would allow reusing 100% of the existing logic, and remove the need
to export file_system_type nsfs;
As your test exists below it will reject a lot more than mount namespace
file descriptors. It will reject file descriptors for every other
namespace as well.
Eric
> ---
> commit 069c3376f7849044117c866aeafbb1a525f84926
> Author: David Howells <dhowells@redhat.com>
> Date: Thu Oct 4 23:18:59 2018 +0100
>
> fixes
>
> diff --git a/fs/internal.h b/fs/internal.h
> index 17029b30e196..47a6c80c3c51 100644
> --- a/fs/internal.h
> +++ b/fs/internal.h
> @@ -172,6 +172,7 @@ extern void mnt_pin_kill(struct mount *m);
> * fs/nsfs.c
> */
> extern const struct dentry_operations ns_dentry_operations;
> +extern struct file_system_type nsfs;
>
> /*
> * fs/ioctl.c
> diff --git a/fs/namespace.c b/fs/namespace.c
> index e969ded7d54b..25ecd8b3c76b 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -2388,6 +2388,27 @@ static inline int tree_contains_unbindable(struct mount *mnt)
> return 0;
> }
>
> +/*
> + * Object if there are any nsfs mounts in the specified subtree. These can act
> + * as pins for mount namespaces that aren't checked by the mount-cycle checking
> + * code, thereby allowing cycles to be made.
> + */
> +static bool check_for_nsfs_mounts(struct mount *subtree)
> +{
> + struct mount *p;
> + bool ret = false;
> +
> + lock_mount_hash();
> + for (p = subtree; p; p = next_mnt(p, subtree))
> + if (p->mnt.mnt_sb->s_type == &nsfs)
> + goto out;
> +
> + ret = true;
> +out:
> + unlock_mount_hash();
> + return ret;
> +}
> +
> static int do_move_mount(struct path *old_path, struct path *new_path)
> {
> struct path parent_path = {.mnt = NULL, .dentry = NULL};
> @@ -2442,6 +2463,8 @@ static int do_move_mount(struct path *old_path, struct path *new_path)
> if (IS_MNT_SHARED(p) && tree_contains_unbindable(old))
> goto out1;
> err = -ELOOP;
> + if (!check_for_nsfs_mounts(old))
> + goto out1;
> for (; mnt_has_parent(p); p = p->mnt_parent)
> if (p == old)
> goto out1;
> diff --git a/fs/nsfs.c b/fs/nsfs.c
> index f069eb6495b0..d3abcd5c2a23 100644
> --- a/fs/nsfs.c
> +++ b/fs/nsfs.c
> @@ -269,7 +269,7 @@ static struct dentry *nsfs_mount(struct file_system_type *fs_type,
> return mount_pseudo(fs_type, "nsfs:", &nsfs_ops,
> &ns_dentry_operations, NSFS_MAGIC);
> }
> -static struct file_system_type nsfs = {
> +struct file_system_type nsfs = {
> .name = "nsfs",
> .mount = nsfs_mount,
> .kill_sb = kill_anon_super,
next prev parent reply other threads:[~2018-10-11 18:38 UTC|newest]
Thread overview: 98+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-21 16:30 [PATCH 00/34] VFS: Introduce filesystem context [ver #12] David Howells
2018-09-21 16:30 ` [PATCH 01/34] vfs: syscall: Add open_tree(2) to reference or clone a mount " David Howells
2018-10-21 16:41 ` Eric W. Biederman
2018-09-21 16:30 ` [PATCH 02/34] vfs: syscall: Add move_mount(2) to move mounts around " David Howells
2018-09-21 16:30 ` [PATCH 03/34] teach move_mount(2) to work with OPEN_TREE_CLONE " David Howells
2018-10-05 18:24 ` Alan Jenkins
2018-10-07 10:48 ` Alan Jenkins
2018-10-07 19:20 ` Alan Jenkins
2018-10-10 12:36 ` David Howells
2018-10-12 14:22 ` Alan Jenkins
2018-10-12 14:54 ` David Howells
2018-10-12 14:57 ` Alan Jenkins
2018-10-11 9:17 ` David Howells
2018-10-11 11:48 ` Alan Jenkins
2018-10-11 13:10 ` David Howells
2018-10-11 12:14 ` David Howells
2018-10-11 12:23 ` Alan Jenkins
2018-10-11 15:33 ` David Howells
2018-10-11 18:38 ` Eric W. Biederman [this message]
2018-10-11 20:17 ` David Howells
2018-10-13 6:06 ` Al Viro
2018-10-17 17:45 ` Alan Jenkins
2018-10-18 20:09 ` David Howells
2018-10-18 20:58 ` David Howells
2018-10-19 11:57 ` David Howells
2018-10-19 13:37 ` David Howells
2018-10-19 17:35 ` Alan Jenkins
2018-10-19 21:35 ` David Howells
2018-10-19 21:40 ` David Howells
2018-10-19 22:36 ` David Howells
2018-10-20 5:25 ` Al Viro
2018-10-20 11:06 ` Alan Jenkins
2018-10-20 11:48 ` Al Viro
2018-10-20 12:26 ` Al Viro
2018-10-21 0:40 ` David Howells
2018-10-10 11:56 ` David Howells
2018-10-10 12:31 ` David Howells
2018-10-10 12:39 ` Alan Jenkins
2018-10-10 12:50 ` David Howells
2018-10-10 13:02 ` David Howells
2018-10-10 13:06 ` Alan Jenkins
2018-10-21 16:57 ` Eric W. Biederman
2018-10-23 11:19 ` Alan Jenkins
2018-10-23 16:22 ` Al Viro
2018-09-21 16:30 ` [PATCH 04/34] vfs: Suppress MS_* flag defs within the kernel unless explicitly enabled " David Howells
2018-09-21 16:30 ` [PATCH 05/34] vfs: Introduce the basic header for the new mount API's filesystem context " David Howells
2018-09-21 16:30 ` [PATCH 06/34] vfs: Introduce logging functions " David Howells
2018-09-21 16:31 ` [PATCH 07/34] vfs: Add configuration parser helpers " David Howells
2019-03-14 7:46 ` Geert Uytterhoeven
2019-03-14 10:27 ` David Howells
2019-03-14 10:49 ` Geert Uytterhoeven
2018-09-21 16:31 ` [PATCH 08/34] vfs: Add LSM hooks for the new mount API " David Howells
2018-09-21 16:31 ` [PATCH 09/34] vfs: Put security flags into the fs_context struct " David Howells
2018-09-21 16:31 ` [PATCH 10/34] selinux: Implement the new mount API LSM hooks " David Howells
2018-09-21 16:31 ` [PATCH 11/34] smack: Implement filesystem context security " David Howells
2018-09-21 16:31 ` [PATCH 12/34] apparmor: Implement security hooks for the new mount API " David Howells
2018-09-21 16:31 ` [PATCH 13/34] tomoyo: " David Howells
2018-09-21 16:32 ` [PATCH 14/34] vfs: Separate changing mount flags full remount " David Howells
2018-09-21 16:32 ` [PATCH 15/34] vfs: Implement a filesystem superblock creation/configuration context " David Howells
2018-09-21 16:32 ` [PATCH 16/34] vfs: Remove unused code after filesystem context changes " David Howells
2018-09-21 16:32 ` [PATCH 17/34] procfs: Move proc_fill_super() to fs/proc/root.c " David Howells
2018-09-21 16:32 ` [PATCH 18/34] proc: Add fs_context support to procfs " David Howells
2018-09-21 16:32 ` [PATCH 19/34] ipc: Convert mqueue fs to fs_context " David Howells
2018-09-21 16:32 ` [PATCH 20/34] cpuset: Use " David Howells
2018-09-21 16:33 ` [PATCH 21/34] kernfs, sysfs, cgroup, intel_rdt: Support " David Howells
2018-11-19 4:23 ` Andrei Vagin
2018-12-06 17:08 ` Andrei Vagin
2018-09-21 16:33 ` [PATCH 22/34] hugetlbfs: Convert to " David Howells
2018-09-21 16:33 ` [PATCH 23/34] vfs: Remove kern_mount_data() " David Howells
2018-09-21 16:33 ` [PATCH 24/34] vfs: Provide documentation for new mount API " David Howells
2018-09-21 16:33 ` [PATCH 25/34] Make anon_inodes unconditional " David Howells
2018-09-21 16:33 ` [PATCH 26/34] vfs: syscall: Add fsopen() to prepare for superblock creation " David Howells
2018-09-21 16:33 ` [PATCH 27/34] vfs: Implement logging through fs_context " David Howells
2018-09-21 16:33 ` [PATCH 28/34] vfs: Add some logging to the core users of the fs_context log " David Howells
2018-09-21 16:34 ` [PATCH 29/34] vfs: syscall: Add fsconfig() for configuring and managing a context " David Howells
2018-09-21 16:34 ` [PATCH 30/34] vfs: syscall: Add fsmount() to create a mount for a superblock " David Howells
2018-09-21 16:34 ` [PATCH 31/34] vfs: syscall: Add fspick() to select a superblock for reconfiguration " David Howells
2018-10-12 14:49 ` Alan Jenkins
2018-10-13 6:11 ` Al Viro
2018-10-13 9:45 ` Alan Jenkins
2018-10-13 23:04 ` Andy Lutomirski
2018-10-17 13:15 ` David Howells
2018-10-17 13:20 ` David Howells
2018-10-17 14:31 ` Alan Jenkins
2018-10-17 14:35 ` Eric W. Biederman
2018-10-17 14:55 ` Alan Jenkins
2018-10-17 15:24 ` David Howells
2018-10-17 15:38 ` Eric W. Biederman
2018-10-17 15:45 ` David Howells
2018-10-17 17:41 ` Alan Jenkins
2018-10-17 21:20 ` David Howells
2018-10-17 22:13 ` Alan Jenkins
2018-09-21 16:34 ` [PATCH 32/34] afs: Add fs_context support " David Howells
2018-09-21 16:34 ` [PATCH 33/34] afs: Use fs_context to pass parameters over automount " David Howells
2018-09-21 16:34 ` [PATCH 34/34] vfs: Add a sample program for the new mount API " David Howells
2018-12-17 14:12 ` Anders Roxell
2018-12-20 16:36 ` David Howells
2018-10-04 18:37 ` [PATCH 00/34] VFS: Introduce filesystem context " Eric W. Biederman
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