Linux-Fsdevel Archive on lore.kernel.org
 help / Atom feed
* [PATCH] fs: add a comment explaining how MNT_NS_INTERNAL affects mnt_may_suid()
@ 2018-11-21 19:58 Jann Horn
  2019-02-04  4:04 ` Jann Horn
  0 siblings, 1 reply; 2+ messages in thread
From: Jann Horn @ 2018-11-21 19:58 UTC (permalink / raw)
  To: Alexander Viro, jannh; +Cc: Andy Lutomirski, linux-kernel, linux-fsdevel

commit 380cf5ba6b0a ("fs: Treat foreign mounts as nosuid"), in addition to
the intended effect, also prevented suid execution of memfd files.
(And I think that's a good change.)

Signed-off-by: Jann Horn <jannh@google.com>
---
 fs/namespace.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/namespace.c b/fs/namespace.c
index a7f91265ea67..e68488426e42 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3400,6 +3400,9 @@ bool mnt_may_suid(struct vfsmount *mnt)
 	 * prevents namespaces from trusting potentially unsafe
 	 * suid/sgid bits, file caps, or security labels that originate
 	 * in other namespaces.
+	 *
+	 * check_mnt() rejects MNT_NS_INTERNAL mounts; this means that suid
+	 * execution is blocked for files on internal mounts, e.g. memfds.
 	 */
 	return !(mnt->mnt_flags & MNT_NOSUID) && check_mnt(real_mount(mnt)) &&
 	       current_in_userns(mnt->mnt_sb->s_user_ns);
-- 
2.20.0.rc0.387.gc7a69e6b6c-goog

^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH] fs: add a comment explaining how MNT_NS_INTERNAL affects mnt_may_suid()
  2018-11-21 19:58 [PATCH] fs: add a comment explaining how MNT_NS_INTERNAL affects mnt_may_suid() Jann Horn
@ 2019-02-04  4:04 ` Jann Horn
  0 siblings, 0 replies; 2+ messages in thread
From: Jann Horn @ 2019-02-04  4:04 UTC (permalink / raw)
  To: Alexander Viro, Jann Horn; +Cc: Andy Lutomirski, kernel list, linux-fsdevel

On Wed, Nov 21, 2018 at 8:59 PM Jann Horn <jannh@google.com> wrote:
> commit 380cf5ba6b0a ("fs: Treat foreign mounts as nosuid"), in addition to
> the intended effect, also prevented suid execution of memfd files.
> (And I think that's a good change.)

Ping. Al, can you take this into your tree? fs/namespace.c is your stuff, right?


> Signed-off-by: Jann Horn <jannh@google.com>
> ---
>  fs/namespace.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/fs/namespace.c b/fs/namespace.c
> index a7f91265ea67..e68488426e42 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -3400,6 +3400,9 @@ bool mnt_may_suid(struct vfsmount *mnt)
>          * prevents namespaces from trusting potentially unsafe
>          * suid/sgid bits, file caps, or security labels that originate
>          * in other namespaces.
> +        *
> +        * check_mnt() rejects MNT_NS_INTERNAL mounts; this means that suid
> +        * execution is blocked for files on internal mounts, e.g. memfds.
>          */
>         return !(mnt->mnt_flags & MNT_NOSUID) && check_mnt(real_mount(mnt)) &&
>                current_in_userns(mnt->mnt_sb->s_user_ns);
> --
> 2.20.0.rc0.387.gc7a69e6b6c-goog
>

^ permalink raw reply	[flat|nested] 2+ messages in thread

end of thread, back to index

Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-11-21 19:58 [PATCH] fs: add a comment explaining how MNT_NS_INTERNAL affects mnt_may_suid() Jann Horn
2019-02-04  4:04 ` Jann Horn

Linux-Fsdevel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-fsdevel/0 linux-fsdevel/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-fsdevel linux-fsdevel/ https://lore.kernel.org/linux-fsdevel \
		linux-fsdevel@vger.kernel.org linux-fsdevel@archiver.kernel.org
	public-inbox-index linux-fsdevel


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-fsdevel


AGPL code for this site: git clone https://public-inbox.org/ public-inbox