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    SubjectRe: [PATCH] tmpfs: security xattr setting on inode creation
    From
    Hi Hugh,

    On Sat, Feb 25, 2012 at 5:19 AM, Hugh Dickins <hughd@google.com> wrote:
    > Thanks a lot for doing this, Jarkko: I knew nothing about it.
    > And thank you James for reviewing, I felt much happier seeing that.
    >
    > I did fiddle around with it slightly, to reduce the added textsize,
    > and eliminate it when CONFIG_TMPFS_XATTR is off.  Please, Jarkko
    > and James, complain bitterly if I've messed up the good work.

    Thank you for the nice feedback :) LGTM.

    >
    > [PATCH] tmpfs: security xattr setting on inode creation
    >
    > From: Jarkko Sakkinen <jarkko.sakkinen@intel.com>
    >
    > Adds to generic xattr support introduced in Linux 3.0 by
    > implementing initxattrs callback. This enables consulting
    > of security attributes from LSM and EVM when inode is created.
    >
    > [hughd: moved under CONFIG_TMPFS_XATTR, with memcpy in shmem_xattr_alloc]
    >
    > Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@intel.com>
    > Reviewed-by: James Morris <james.l.morris@oracle.com>
    > Signed-off-by: Hugh Dickins <hughd@google.com>
    > ---
    >  mm/shmem.c |   88 +++++++++++++++++++++++++++++++++++++++++----------
    >  1 file changed, 72 insertions(+), 16 deletions(-)
    >
    > --- a/mm/shmem.c
    > +++ b/mm/shmem.c
    > @@ -1178,6 +1178,12 @@ static struct inode *shmem_get_inode(str
    >  static const struct inode_operations shmem_symlink_inode_operations;
    >  static const struct inode_operations shmem_short_symlink_operations;
    >
    > +#ifdef CONFIG_TMPFS_XATTR
    > +static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
    > +#else
    > +#define shmem_initxattrs NULL
    > +#endif
    > +
    >  static int
    >  shmem_write_begin(struct file *file, struct address_space *mapping,
    >                        loff_t pos, unsigned len, unsigned flags,
    > @@ -1490,7 +1496,7 @@ shmem_mknod(struct inode *dir, struct de
    >        if (inode) {
    >                error = security_inode_init_security(inode, dir,
    >                                                     &dentry->d_name,
    > -                                                    NULL, NULL);
    > +                                                    shmem_initxattrs, NULL);
    >                if (error) {
    >                        if (error != -EOPNOTSUPP) {
    >                                iput(inode);
    > @@ -1630,7 +1636,7 @@ static int shmem_symlink(struct inode *d
    >                return -ENOSPC;
    >
    >        error = security_inode_init_security(inode, dir, &dentry->d_name,
    > -                                            NULL, NULL);
    > +                                            shmem_initxattrs, NULL);
    >        if (error) {
    >                if (error != -EOPNOTSUPP) {
    >                        iput(inode);
    > @@ -1704,6 +1710,66 @@ static void shmem_put_link(struct dentry
    >  * filesystem level, though.
    >  */
    >
    > +/*
    > + * Allocate new xattr and copy in the value; but leave the name to callers.
    > + */
    > +static struct shmem_xattr *shmem_xattr_alloc(const void *value, size_t size)
    > +{
    > +       struct shmem_xattr *new_xattr;
    > +       size_t len;
    > +
    > +       /* wrap around? */
    > +       len = sizeof(*new_xattr) + size;
    > +       if (len <= sizeof(*new_xattr))
    > +               return NULL;
    > +
    > +       new_xattr = kmalloc(len, GFP_KERNEL);
    > +       if (!new_xattr)
    > +               return NULL;
    > +
    > +       new_xattr->size = size;
    > +       memcpy(new_xattr->value, value, size);
    > +       return new_xattr;
    > +}
    > +
    > +/*
    > + * 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;
    > +}
    > +
    >  static int shmem_xattr_get(struct dentry *dentry, const char *name,
    >                           void *buffer, size_t size)
    >  {
    > @@ -1731,24 +1797,17 @@ static int shmem_xattr_get(struct dentry
    >        return ret;
    >  }
    >
    > -static int shmem_xattr_set(struct dentry *dentry, const char *name,
    > +static int shmem_xattr_set(struct inode *inode, const char *name,
    >                           const void *value, size_t size, int flags)
    >  {
    > -       struct inode *inode = dentry->d_inode;
    >        struct shmem_inode_info *info = SHMEM_I(inode);
    >        struct shmem_xattr *xattr;
    >        struct shmem_xattr *new_xattr = NULL;
    > -       size_t len;
    >        int err = 0;
    >
    >        /* value == NULL means remove */
    >        if (value) {
    > -               /* wrap around? */
    > -               len = sizeof(*new_xattr) + size;
    > -               if (len <= sizeof(*new_xattr))
    > -                       return -ENOMEM;
    > -
    > -               new_xattr = kmalloc(len, GFP_KERNEL);
    > +               new_xattr = shmem_xattr_alloc(value, size);
    >                if (!new_xattr)
    >                        return -ENOMEM;
    >
    > @@ -1757,9 +1816,6 @@ static int shmem_xattr_set(struct dentry
    >                        kfree(new_xattr);
    >                        return -ENOMEM;
    >                }
    > -
    > -               new_xattr->size = size;
    > -               memcpy(new_xattr->value, value, size);
    >        }
    >
    >        spin_lock(&info->lock);
    > @@ -1858,7 +1914,7 @@ static int shmem_setxattr(struct dentry
    >        if (size == 0)
    >                value = "";  /* empty EA, do not remove */
    >
    > -       return shmem_xattr_set(dentry, name, value, size, flags);
    > +       return shmem_xattr_set(dentry->d_inode, name, value, size, flags);
    >
    >  }
    >
    > @@ -1878,7 +1934,7 @@ static int shmem_removexattr(struct dent
    >        if (err)
    >                return err;
    >
    > -       return shmem_xattr_set(dentry, name, NULL, 0, XATTR_REPLACE);
    > +       return shmem_xattr_set(dentry->d_inode, name, NULL, 0, XATTR_REPLACE);
    >  }
    >
    >  static bool xattr_is_trusted(const char *name)

    /Jarkko
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      Last update: 2012-02-25 08:07    [W:0.036 / U:29.552 seconds]
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