linux-kernel - Re: [bug] /etc/profile: line 30: /dev/null: Permission denied

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Message-ID: <m14or0vul4.fsf@fess.ebiederm.org>
Date:	Fri, 18 Sep 2009 13:58:15 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Kay Sievers <kay.sievers@...y.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, Greg KH <greg@...ah.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [bug] /etc/profile: line 30: /dev/null: Permission denied

As a special case you can implement this much
more simply in devtmpfs_mount just do:

int devtmpfs_mount(const char *mountpoint)
{
        sys_mount("none", "dev", "devtmpfs", MS_SILENT, NULL);
	sys_chmod("dev/console", 0666);
	sys_chmod("dev/tty", 0666);
	sys_chmod("dev/null", 0666);
	sys_chmod("dev/zero", 0666);
}

Not using sys_mount is the problem Christoph was complaining about.

Grafting dev_mount into the global namespace (instead of making
a copy and grafting that is pretty hideous).   It means that
vfs_path_lookup will follow mounts, and it is a reference counting
problem.  You can probably oops the kernel by going into single
user mode and unmounting devtmpfs as the code stands right now.

Eric

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