linux-kernel - Re: [PATCH] tmpfs: security xattr setting on inode creation

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Message-ID: <CAGGTEhP=jbA664fbbZaVEN5Bxq9_3iiV84ME8QSTUohv2JLkqw@mail.gmail.com>
Date:	Tue, 28 Feb 2012 12:46:13 +0900
From:	"Ware, Ryan R" <ryan.r.ware@...el.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Hugh Dickins <hughd@...gle.com>,
	Jarkko Sakkinen <jarkko.sakkinen@...el.com>,
	James Morris <jmorris@...ei.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org
Subject: Re: [PATCH] tmpfs: security xattr setting on inode creation

On Tue, Feb 28, 2012 at 7:46 AM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
>
> On Fri, 24 Feb 2012 19:19:22 -0800 (PST)
> Hugh Dickins <hughd@...gle.com> wrote:
>
> > +/*
> > + * Callback for security_inode_init_security() for acquiring xattrs.
> > + */
> > +static int shmem_initxattrs(struct inode *inode,
> > +                         const struct xattr *xattr_array,
> > +                         void *fs_info)
> > +{
> > +     struct shmem_inode_info *info = SHMEM_I(inode);
> > +     const struct xattr *xattr;
> > +     struct shmem_xattr *new_xattr;
> > +     size_t len;
> > +
> > +     for (xattr = xattr_array; xattr->name != NULL; xattr++) {
> > +             new_xattr = shmem_xattr_alloc(xattr->value,
> > xattr->value_len);
> > +             if (!new_xattr)
> > +                     return -ENOMEM;
> > +
> > +             len = strlen(xattr->name) + 1;
> > +             new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
> > +                                       GFP_KERNEL);
> > +             if (!new_xattr->name) {
> > +                     kfree(new_xattr);
> > +                     return -ENOMEM;
> > +             }
> > +
> > +             memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
> > +                    XATTR_SECURITY_PREFIX_LEN);
> > +             memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
> > +                    xattr->name, len);
> > +
> > +             spin_lock(&info->lock);
> > +             list_add(&new_xattr->list, &info->xattr_list);
> > +             spin_unlock(&info->lock);
> > +     }
> > +
> > +     return 0;
> > +}
>
> So if there's a kmalloc failure partway through the array, we leave a
> partially xattrified inode in place.
>
> Are we sure this is OK?

I'm guessing Jarkko can clean that up a bit.  It wouldn't be a good
idea to leave inaccurate data structures laying around during failure
cases.

Ryan
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