From 780dca1b1e1d167e5f795ced691dccd44baa1c75 Mon Sep 17 00:00:00 2001 From: Konstantin Belousov Date: Wed, 27 May 2015 09:22:50 +0000 Subject: [PATCH] Right now, dounmount() is called with unreferenced mount point. Nothing stops a parallel unmount to suceed before the given call to dounmount() checks and locks the covered vnode. Prevent dounmount() from acting on the freed (although type-stable) memory by changing the interface to require the mount point to be referenced. dounmount() consumes the reference on return, regardless of the sucessfull or erronous result. Tested by: pho Sponsored by: The FreeBSD Foundation MFC after: 2 weeks --- .../uts/common/fs/zfs/zfs_ctldir.c | 1 + .../opensolaris/uts/common/fs/zfs/zfs_ioctl.c | 1 + .../uts/common/fs/zfs/zfs_vfsops.c | 1 + sys/kern/vfs_mount.c | 30 +++++++++---------- sys/kern/vfs_subr.c | 3 +- 5 files changed, 20 insertions(+), 16 deletions(-) diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ctldir.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ctldir.c index 9e0b8a0998c3..c2dd020b4c0d 100644 --- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ctldir.c +++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ctldir.c @@ -697,6 +697,7 @@ zfsctl_unmount_snap(zfs_snapentry_t *sep, int fflags, cred_t *cr) return (0); #else + vfs_ref(vn_mountedvfs(svp)); return (dounmount(vn_mountedvfs(svp), fflags, curthread)); #endif } diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c index d4291ec8d30d..5800db0c310b 100644 --- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c +++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ioctl.c @@ -3481,6 +3481,7 @@ zfs_unmount_snap(const char *snapname) #ifdef illumos (void) dounmount(vfsp, MS_FORCE, kcred); #else + vfs_ref(vfsp); (void) dounmount(vfsp, MS_FORCE, curthread); #endif return (0); diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c index 5824828c7a07..c44516f175fd 100644 --- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c +++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c @@ -2315,6 +2315,7 @@ bail: * unmount this file system. */ if (vn_vfswlock(zfsvfs->z_vfs->vfs_vnodecovered) == 0) + vfs_ref(zfsvfs->z_vfs); (void) dounmount(zfsvfs->z_vfs, MS_FORCE, curthread); } return (err); diff --git a/sys/kern/vfs_mount.c b/sys/kern/vfs_mount.c index 09fa7ed071bf..c86259b11637 100644 --- a/sys/kern/vfs_mount.c +++ b/sys/kern/vfs_mount.c @@ -1128,12 +1128,7 @@ struct unmount_args { #endif /* ARGSUSED */ int -sys_unmount(td, uap) - struct thread *td; - register struct unmount_args /* { - char *path; - int flags; - } */ *uap; +sys_unmount(struct thread *td, struct unmount_args *uap) { struct nameidata nd; struct mount *mp; @@ -1164,8 +1159,10 @@ sys_unmount(td, uap) mtx_lock(&mountlist_mtx); TAILQ_FOREACH_REVERSE(mp, &mountlist, mntlist, mnt_list) { if (mp->mnt_stat.f_fsid.val[0] == id0 && - mp->mnt_stat.f_fsid.val[1] == id1) + mp->mnt_stat.f_fsid.val[1] == id1) { + vfs_ref(mp); break; + } } mtx_unlock(&mountlist_mtx); } else { @@ -1183,8 +1180,10 @@ sys_unmount(td, uap) } mtx_lock(&mountlist_mtx); TAILQ_FOREACH_REVERSE(mp, &mountlist, mntlist, mnt_list) { - if (strcmp(mp->mnt_stat.f_mntonname, pathbuf) == 0) + if (strcmp(mp->mnt_stat.f_mntonname, pathbuf) == 0) { + vfs_ref(mp); break; + } } mtx_unlock(&mountlist_mtx); } @@ -1202,8 +1201,10 @@ sys_unmount(td, uap) /* * Don't allow unmounting the root filesystem. */ - if (mp->mnt_flag & MNT_ROOTFS) + if (mp->mnt_flag & MNT_ROOTFS) { + vfs_rel(mp); return (EINVAL); + } error = dounmount(mp, uap->flags, td); return (error); } @@ -1212,10 +1213,7 @@ sys_unmount(td, uap) * Do the actual filesystem unmount. */ int -dounmount(mp, flags, td) - struct mount *mp; - int flags; - struct thread *td; +dounmount(struct mount *mp, int flags, struct thread *td) { struct vnode *coveredvp, *fsrootvp; int error; @@ -1235,6 +1233,7 @@ dounmount(mp, flags, td) if (coveredvp->v_mountedhere != mp || coveredvp->v_mountedhere->mnt_gen != mnt_gen_r) { VOP_UNLOCK(coveredvp, 0); + vfs_rel(mp); return (EBUSY); } } @@ -1243,13 +1242,14 @@ dounmount(mp, flags, td) * original mount is permitted to unmount this filesystem. */ error = vfs_suser(mp, td); - if (error) { + if (error != 0) { if (coveredvp) VOP_UNLOCK(coveredvp, 0); + vfs_rel(mp); return (error); } - vn_start_write(NULL, &mp, V_WAIT); + vn_start_write(NULL, &mp, V_WAIT | V_MNTREF); MNT_ILOCK(mp); if ((mp->mnt_kern_flag & MNTK_UNMOUNT) != 0 || !TAILQ_EMPTY(&mp->mnt_uppers)) { diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c index 8e34456621ca..625d193b2c1b 100644 --- a/sys/kern/vfs_subr.c +++ b/sys/kern/vfs_subr.c @@ -3502,8 +3502,9 @@ vfs_unmountall(void) */ while(!TAILQ_EMPTY(&mountlist)) { mp = TAILQ_LAST(&mountlist, mntlist); + vfs_ref(mp); error = dounmount(mp, MNT_FORCE, td); - if (error) { + if (error != 0) { TAILQ_REMOVE(&mountlist, mp, mnt_list); /* * XXX: Due to the way in which we mount the root