linux-kernel - Re: [PATCH] afs: proc cells and rootcell are writeable

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Message-ID: <3349.1391128281@warthog.procyon.org.uk>
Date:	Fri, 31 Jan 2014 00:31:21 +0000
From:	David Howells <dhowells@...hat.com>
To:	unlisted-recipients:; (no To-header on input)
Cc:	dhowells@...hat.com,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-afs@...ts.infradead.org,
	Pali Rohár <pali.rohar@...il.com>
Subject: Re: [PATCH] afs: proc cells and rootcell are writeable

David Howells <dhowells@...hat.com> wrote:

> > > I think this is a pretty strong argument. Counter-arguments, anybody?
> > 
> > Yes.  CAP_DAC_READ_SEARCH.
> 
> No, it would seem unlikely it's that, but I guess there's another capability
> override because the process is owned by root.

CAP_DAC_OVERRIDE, I think.

	int generic_permission(struct inode *inode, int mask)
	{
	...
		/*
		 * Read/write DACs are always overridable.
		 * Executable DACs are overridable when there is
		 * at least one exec bit set.
		 */
		if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
			if (inode_capable(inode, CAP_DAC_OVERRIDE))
				return 0;
	...
	}

David
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