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	Tue, 02 Jun 2026 14:07:51 +0000
Date: Tue, 2 Jun 2026 15:07:51 +0100
From: Al Viro <viro@zeniv.linux.org.uk>
To: Jan Kara <jack@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Christian Brauner <brauner@kernel.org>,
	linux-fsdevel@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
	lvc-project@linuxtesting.org, stable@vger.kernel.org,
	Denis Arefev <arefev@swemel.ru>
Subject: Re: [PATCH] make new mount API honour SB_NOUSER (was Re: [PATCH]
 block: Avoid mounting the bdev pseudo-filesystem in userspace)
Message-ID: <20260602140751.GS2636677@ZenIV>
References: <20260521072857.5078-1-arefev@swemel.ru>
 <20260602011907.GM2636677@ZenIV>
 <20260602013526.GO2636677@ZenIV>
 <20260602020444.GP2636677@ZenIV>
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Sender: Al Viro <viro@ftp.linux.org.uk>

On Tue, Jun 02, 2026 at 11:11:11AM +0200, Jan Kara wrote:
> On Tue 02-06-26 03:04:44, Al Viro wrote:
> > one should *not* be allowed to mount one of those, new API or not.
> > 
> > Reported-by: Denis Arefev <arefev@swemel.ru>
> > Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
> 
> Won't it make sense to actually check fc->sb_flags before we call
> vfs_create_mount()? Otherwise it looks good to me.

Interpretation of fc->sb_flags is up to your ->get_tree().  What matters
is ->s_flags in the resulting superblock; that's type-independent and
that's what we ought to check...