linux-kernel - Re: Reiserfs.c bug in 3.2-rc5

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Date:	Tue, 03 Jan 2012 17:28:36 -0500
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Jan Kara <jack@...e.cz>, linux-kernel@...r.kernel.org,
	reiserfs-devel@...r.kernel.org, haiyangz@...rosoft.com,
	hjanssen@...rosoft.com, "Rafael J. Wysocki" <rjw@...k.pl>,
	James Morris <jmorris@...ei.org>,
	Jorge Bastos <mysql.jorge@...imal.pt>,
	Mark Fasheh <mfasheh@...e.com>,
	Joel Becker <jlbec@...lplan.org>
Subject: Re: Reiserfs.c bug in 3.2-rc5

On Tue, 2012-01-03 at 11:17 -0800, Linus Torvalds wrote:
> On Tue, Jan 3, 2012 at 10:45 AM, Mimi Zohar <zohar@...ux.vnet.ibm.com> wrote:
> >
> > Just clarifying not all of commit fb88c2b, but only the
> > security_old_inode_init_security() hunk.
> 
> Is it really sane to have different semantics like that for the
> security[_old]_inode_init_security functions?

No, but unfortunately it seems necessary.

> Look at ocfs2, for example: it does nothing if
> ocfs2_init_security_get() returns 0. That does not sound like the
> correct thing to do, when the fallback is to do ocfs2_init_acl() under
> the lock.

The original code did the same for -EOPNOTSUPP.

7192        ret = ocfs2_init_security_get(inode, dir, qstr, &si);
7193        if (!ret) {
7194                ret = ocfs2_xattr_set(inode, OCFS2_XATTR_INDEX_SECURITY,
7195                                      si.name, si.value, si.value_len,
7196                                      XATTR_CREATE);
7197                if (ret) {
7198                        mlog_errno(ret);
7199                        goto leave;
7200                }
7201        } else if (ret != -EOPNOTSUPP) {
7202                mlog_errno(ret);
7203                goto leave;
7204        }
7205
7206        ret = ocfs2_inode_lock(dir, &dir_bh, 0);
7207        if (ret) {
7208                mlog_errno(ret);
7209                goto leave;
7210        }
7211
7212        ret = ocfs2_init_acl(NULL, inode, dir, NULL, dir_bh, NULL, NULL);
7213        if (ret)
7214                mlog_errno(ret);
7215

> And ocfs2_init_security_get() just calls either
> security_inode_init_security() or security_old_inode_init_security()
> depending on whether ocfs2_security_xattr_info is NULL or not. So I
> really think callers expect the same kind of semantics regardless of
> whether it's the "old" or not version. Which would make sense anyway.
> 
> Also, the *documentation* in include/linux/security.h very much says
> that it returns 0 only if @name and @value have been successfully set.
> So my gut feel says that both security_inode_init_security and
> security_old_inode_init_security should return -EOPNOTSUPP (although
> the "new" version doesn't really have "name/value", so maybe returning
> 0 is ok)

The original security_inode_init_security() version queried the LSM for
the security xattr, leaving writing the xattr up to the caller.  The
caller changed -EOPNPTSUPP to 0, before returning.  The new version
combines the querying and writing the xattr.  Like the previous version
it converts the -EOPNOTSUPP to 0, before returning.

reiserfs_security_init() is dependent on
security_old_inode_init_security() to return -EOPNOTSUPP to initialize
some variables and return, but before returning it changes -EOPNOTSUPP
to 0.

Unfortunately this leaves security_old/security_inode_init_security()
needing to return different things.

Mimi

> Anyway, I'd love for (multiple) people who really know the code to
> give me a clean agreement on exactly what the correct patch is.
> Please?
> 
>                                  Linus
> 


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