On Thu, Dec 07, 2017 at 11:31:51AM -0600, Bill O'Donnell wrote:
> On Mon, Aug 14, 2017 at 05:18:10AM -0300, Ernesto A. Fernández wrote:
> > When changing a file's ACL mask, xfs_set_acl() will first set the group
> > bits of i_mode to the value of the mask, and only then set the actual
> > extended attribute representing the new ACL.
> >
> > If the second part fails (due to lack of space, for example) and the
> > file had no ACL attribute to begin with, the system will from now on
> > assume that the mask permission bits are actual group permission bits,
> > potentially granting access to the wrong users.
> >
> > To prevent this, perform the mode update and the ACL update as part of
> > the same transaction, and restore the original mode to the vfs inode in
> > case of failure. This requires a change in how extended attributes are
> > deleted: commit the transaction even if there was no attribute to
> > remove, to log the standard inode fields.
> >
> > Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@xxxxxxxxx>
> > ---
> > This issue is covered by generic/449 in xfstests. Several other filesystems
>
> Sorry, I'm coming into this late, and might be missing something...
> is there a particular xfs configuration that you've set up on which
> generic/449 fails? On 4.15-rc1, I see no failures of g/449.
Fixed in:
67f2ffe31d1 ("xfs: don't change inode mode if ACL update fails")
(I think...)
--D
> Thanks-
> Bill
>
>
>
> > are affected by this, some of them have already applied patches:
> > - 397e434 ext4: preserve i_mode if __ext4_set_acl() fails
> > - f070e5a jfs: preserve i_mode if __jfs_set_acl() fails
> > - fcea8ae reiserfs: preserve i_mode if __reiserfs_set_acl() fails
> > - fe26569 ext2: preserve i_mode if ext2_set_acl() fails
> > The test won't exactly pass after this patch is applied. It will fail
> > differently, this time claiming that the filesystem is inconsistent. This
> > probably has something to do with setting too many extended attributes, as
> > it goes away if you change the attribute size in the test from 1k to 64k.
> >
> > fs/xfs/libxfs/xfs_attr.c | 13 +++++++++++--
> > fs/xfs/xfs_acl.c | 39 ++++++++++++++-------------------------
> > 2 files changed, 25 insertions(+), 27 deletions(-)
> >
> > diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> > index de7b9bd..c3193e1 100644
> > --- a/fs/xfs/libxfs/xfs_attr.c
> > +++ b/fs/xfs/libxfs/xfs_attr.c
> > @@ -395,6 +395,7 @@ xfs_attr_remove(
> > struct xfs_defer_ops dfops;
> > xfs_fsblock_t firstblock;
> > int error;
> > + int noattr = 0;
> >
> > XFS_STATS_INC(mp, xs_attr_remove);
> >
> > @@ -438,7 +439,12 @@ xfs_attr_remove(
> > xfs_trans_ijoin(args.trans, dp, 0);
> >
> > if (!xfs_inode_hasattr(dp)) {
> > - error = -ENOATTR;
> > + /*
> > + * Commit even if there is no attr to remove, because when
> > + * setting ACLs the caller may be changing the mode in the
> > + * same transaction.
> > + */
> > + noattr = 1;
> > } else if (dp->i_d.di_aformat == XFS_DINODE_FMT_LOCAL) {
> > ASSERT(dp->i_afp->if_flags & XFS_IFINLINE);
> > error = xfs_attr_shortform_remove(&args);
> > @@ -458,7 +464,7 @@ xfs_attr_remove(
> > if (mp->m_flags & XFS_MOUNT_WSYNC)
> > xfs_trans_set_sync(args.trans);
> >
> > - if ((flags & ATTR_KERNOTIME) == 0)
> > + if ((flags & ATTR_KERNOTIME) == 0 && !noattr)
> > xfs_trans_ichgtime(args.trans, dp, XFS_ICHGTIME_CHG);
> >
> > /*
> > @@ -468,6 +474,9 @@ xfs_attr_remove(
> > error = xfs_trans_commit(args.trans);
> > xfs_iunlock(dp, XFS_ILOCK_EXCL);
> >
> > + if (!error && noattr)
> > + error = -ENOATTR;
> > +
> > return error;
> >
> > out:
> > diff --git a/fs/xfs/xfs_acl.c b/fs/xfs/xfs_acl.c
> > index 7034e17..1fe4363 100644
> > --- a/fs/xfs/xfs_acl.c
> > +++ b/fs/xfs/xfs_acl.c
> > @@ -226,28 +226,13 @@ __xfs_set_acl(struct inode *inode, struct posix_acl *acl, int type)
> > return error;
> > }
> >
> > -static int
> > -xfs_set_mode(struct inode *inode, umode_t mode)
> > -{
> > - int error = 0;
> > -
> > - if (mode != inode->i_mode) {
> > - struct iattr iattr;
> > -
> > - iattr.ia_valid = ATTR_MODE | ATTR_CTIME;
> > - iattr.ia_mode = mode;
> > - iattr.ia_ctime = current_time(inode);
> > -
> > - error = xfs_setattr_nonsize(XFS_I(inode), &iattr, XFS_ATTR_NOACL);
> > - }
> > -
> > - return error;
> > -}
> > -
> > int
> > xfs_set_acl(struct inode *inode, struct posix_acl *acl, int type)
> > {
> > int error = 0;
> > + int mode_changed = 0;
> > + umode_t old_mode = inode->i_mode;
> > + struct timespec old_ctime = inode->i_ctime;
> >
> > if (!acl)
> > goto set_acl;
> > @@ -257,16 +242,20 @@ xfs_set_acl(struct inode *inode, struct posix_acl *acl, int type)
> > return error;
> >
> > if (type == ACL_TYPE_ACCESS) {
> > - umode_t mode;
> > -
> > - error = posix_acl_update_mode(inode, &mode, &acl);
> > - if (error)
> > - return error;
> > - error = xfs_set_mode(inode, mode);
> > + error = posix_acl_update_mode(inode, &inode->i_mode, &acl);
> > if (error)
> > return error;
> > + inode->i_ctime = current_time(inode);
> > + XFS_STATS_INC(XFS_I(inode)->i_mount, xs_ig_attrchg);
> > + mode_changed = 1;
> > }
> >
> > set_acl:
> > - return __xfs_set_acl(inode, acl, type);
> > + error = __xfs_set_acl(inode, acl, type);
> > + if (error && mode_changed) {
> > + inode->i_mode = old_mode;
> > + inode->i_ctime = old_ctime;
> > + XFS_STATS_DEC(XFS_I(inode)->i_mount, xs_ig_attrchg);
> > + }
> > + return error;
> > }
> > --
> > 2.1.4
> >
> > --
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