From 5aa5b278237f356f86205c4b03d4cc64a293850a Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Mon, 12 Jul 2021 12:58:51 -0700 Subject: [PATCH] xfs: don't expose misaligned extszinherit hints to userspace Commit 603f000b15f2 changed xfs_ioctl_setattr_check_extsize to reject an attempt to set an EXTSZINHERIT extent size hint on a directory with RTINHERIT set if the hint isn't a multiple of the realtime extent size. However, I have recently discovered that it is possible to change the realtime extent size when adding a rt device to a filesystem, which means that the existence of directories with misaligned inherited hints is not an accident. As a result, it's possible that someone could have set a valid hint and added an rt volume with a different rt extent size, which invalidates the ondisk hints. After such a sequence, FSGETXATTR will report a misaligned hint, which FSSETXATTR will trip over, causing confusion if the user was doing the usual GET/SET sequence to change some other attribute. Change xfs_fill_fsxattr to omit the hint if it isn't aligned properly. Fixes: 603f000b15f2 ("xfs: validate extsz hints against rt extent size when rtinherit is set") Signed-off-by: Darrick J. Wong Reviewed-by: Christoph Hellwig --- fs/xfs/xfs_ioctl.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c index 275d1c3123bd..16039ea10ac9 100644 --- a/fs/xfs/xfs_ioctl.c +++ b/fs/xfs/xfs_ioctl.c @@ -1065,7 +1065,24 @@ xfs_fill_fsxattr( fileattr_fill_xflags(fa, xfs_ip2xflags(ip)); - fa->fsx_extsize = XFS_FSB_TO_B(mp, ip->i_extsize); + if (ip->i_diflags & XFS_DIFLAG_EXTSIZE) { + fa->fsx_extsize = XFS_FSB_TO_B(mp, ip->i_extsize); + } else if (ip->i_diflags & XFS_DIFLAG_EXTSZINHERIT) { + /* + * Don't let a misaligned extent size hint on a directory + * escape to userspace if it won't pass the setattr checks + * later. + */ + if ((ip->i_diflags & XFS_DIFLAG_RTINHERIT) && + ip->i_extsize % mp->m_sb.sb_rextsize > 0) { + fa->fsx_xflags &= ~(FS_XFLAG_EXTSIZE | + FS_XFLAG_EXTSZINHERIT); + fa->fsx_extsize = 0; + } else { + fa->fsx_extsize = XFS_FSB_TO_B(mp, ip->i_extsize); + } + } + if (ip->i_diflags2 & XFS_DIFLAG2_COWEXTSIZE) fa->fsx_cowextsize = XFS_FSB_TO_B(mp, ip->i_cowextsize); fa->fsx_projid = ip->i_projid;