From f82360acf23145e78cc79aa66f52061c21d7571a Mon Sep 17 00:00:00 2001 From: Konstantin Belousov Date: Sat, 19 Nov 2011 07:50:49 +0000 Subject: [PATCH] Existing VOP_VPTOCNP() interface has a fatal flow that is critical for nullfs. The problem is that resulting vnode is only required to be held on return from the successfull call to vop, instead of being referenced. Nullfs VOP_INACTIVE() method reclaims the vnode, which in combination with the VOP_VPTOCNP() interface means that the directory vnode returned from VOP_VPTOCNP() is reclaimed in advance, causing vn_fullpath() to error with EBADF or like. Change the interface for VOP_VPTOCNP(), now the dvp must be referenced. Convert all in-tree implementations of VOP_VPTOCNP(), which is trivial, because vhold(9) and vref(9) are similar in the locking prerequisites. Out-of-tree fs implementation of VOP_VPTOCNP(), if any, should have no trouble with the fix. Tested by: pho Reviewed by: mckusick MFC after: 3 weeks (subject of re approval) --- .../uts/common/fs/zfs/zfs_ctldir.c | 2 +- sys/fs/devfs/devfs_vnops.c | 4 +- sys/fs/nullfs/null_vnops.c | 7 +- sys/fs/pseudofs/pseudofs_vnops.c | 3 +- sys/kern/vfs_cache.c | 65 ++++++++++++++----- sys/kern/vfs_default.c | 2 +- 6 files changed, 57 insertions(+), 26 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 a880961173c5..65fc902640be 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 @@ -1594,7 +1594,7 @@ zfsctl_snapshot_vptocnp(struct vop_vptocnp_args *ap) *ap->a_buflen -= len; bcopy(sep->se_name, ap->a_buf + *ap->a_buflen, len); mutex_exit(&sdp->sd_lock); - vhold(dvp); + vref(dvp); *ap->a_vpp = dvp; } VN_RELE(dvp); diff --git a/sys/fs/devfs/devfs_vnops.c b/sys/fs/devfs/devfs_vnops.c index eb154b117200..22908b91aa8b 100644 --- a/sys/fs/devfs/devfs_vnops.c +++ b/sys/fs/devfs/devfs_vnops.c @@ -261,7 +261,7 @@ devfs_vptocnp(struct vop_vptocnp_args *ap) } else if (vp->v_type == VDIR) { if (dd == dmp->dm_rootdir) { *dvp = vp; - vhold(*dvp); + vref(*dvp); goto finished; } i -= dd->de_dirent->d_namlen; @@ -289,6 +289,8 @@ devfs_vptocnp(struct vop_vptocnp_args *ap) mtx_unlock(&devfs_de_interlock); vholdl(*dvp); VI_UNLOCK(*dvp); + vref(*dvp); + vdrop(*dvp); } else { mtx_unlock(&devfs_de_interlock); error = ENOENT; diff --git a/sys/fs/nullfs/null_vnops.c b/sys/fs/nullfs/null_vnops.c index 486040437f50..bcf8750fd812 100644 --- a/sys/fs/nullfs/null_vnops.c +++ b/sys/fs/nullfs/null_vnops.c @@ -784,6 +784,7 @@ null_vptocnp(struct vop_vptocnp_args *ap) vhold(lvp); VOP_UNLOCK(vp, 0); /* vp is held by vn_vptocnp_locked that called us */ ldvp = lvp; + vref(lvp); error = vn_vptocnp(&ldvp, cred, ap->a_buf, ap->a_buflen); vdrop(lvp); if (error != 0) { @@ -797,19 +798,17 @@ null_vptocnp(struct vop_vptocnp_args *ap) */ error = vn_lock(ldvp, LK_EXCLUSIVE); if (error != 0) { + vrele(ldvp); vn_lock(vp, locked | LK_RETRY); - vdrop(ldvp); return (ENOENT); } vref(ldvp); - vdrop(ldvp); error = null_nodeget(vp->v_mount, ldvp, dvp); if (error == 0) { #ifdef DIAGNOSTIC NULLVPTOLOWERVP(*dvp); #endif - vhold(*dvp); - vput(*dvp); + VOP_UNLOCK(*dvp, 0); /* keep reference on *dvp */ } else vput(ldvp); diff --git a/sys/fs/pseudofs/pseudofs_vnops.c b/sys/fs/pseudofs/pseudofs_vnops.c index be992b5fde2f..3f0c00e17dea 100644 --- a/sys/fs/pseudofs/pseudofs_vnops.c +++ b/sys/fs/pseudofs/pseudofs_vnops.c @@ -410,8 +410,7 @@ pfs_vptocnp(struct vop_vptocnp_args *ap) } *buflen = i; - vhold(*dvp); - vput(*dvp); + VOP_UNLOCK(*dvp, 0); vn_lock(vp, locked | LK_RETRY); vfs_unbusy(mp); diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c index 11efcab097a0..177fd5602e2f 100644 --- a/sys/kern/vfs_cache.c +++ b/sys/kern/vfs_cache.c @@ -1068,16 +1068,8 @@ vn_vptocnp(struct vnode **vp, struct ucred *cred, char *buf, u_int *buflen) CACHE_RLOCK(); error = vn_vptocnp_locked(vp, cred, buf, buflen); - if (error == 0) { - /* - * vn_vptocnp_locked() dropped hold acquired by - * VOP_VPTOCNP immediately after locking the - * cache. Since we are going to drop the cache rlock, - * re-hold the result. - */ - vhold(*vp); + if (error == 0) CACHE_RUNLOCK(); - } return (error); } @@ -1096,6 +1088,9 @@ vn_vptocnp_locked(struct vnode **vp, struct ucred *cred, char *buf, if (ncp != NULL) { if (*buflen < ncp->nc_nlen) { CACHE_RUNLOCK(); + vfslocked = VFS_LOCK_GIANT((*vp)->v_mount); + vrele(*vp); + VFS_UNLOCK_GIANT(vfslocked); numfullpathfail4++; error = ENOMEM; SDT_PROBE(vfs, namecache, fullpath, return, error, @@ -1106,18 +1101,23 @@ vn_vptocnp_locked(struct vnode **vp, struct ucred *cred, char *buf, memcpy(buf + *buflen, ncp->nc_name, ncp->nc_nlen); SDT_PROBE(vfs, namecache, fullpath, hit, ncp->nc_dvp, ncp->nc_name, vp, 0, 0); + dvp = *vp; *vp = ncp->nc_dvp; + vref(*vp); + CACHE_RUNLOCK(); + vfslocked = VFS_LOCK_GIANT(dvp->v_mount); + vrele(dvp); + VFS_UNLOCK_GIANT(vfslocked); + CACHE_RLOCK(); return (0); } SDT_PROBE(vfs, namecache, fullpath, miss, vp, 0, 0, 0, 0); - vhold(*vp); CACHE_RUNLOCK(); vfslocked = VFS_LOCK_GIANT((*vp)->v_mount); vn_lock(*vp, LK_SHARED | LK_RETRY); error = VOP_VPTOCNP(*vp, &dvp, cred, buf, buflen); - VOP_UNLOCK(*vp, 0); - vdrop(*vp); + vput(*vp); VFS_UNLOCK_GIANT(vfslocked); if (error) { numfullpathfail2++; @@ -1128,16 +1128,20 @@ vn_vptocnp_locked(struct vnode **vp, struct ucred *cred, char *buf, *vp = dvp; CACHE_RLOCK(); - if ((*vp)->v_iflag & VI_DOOMED) { + if (dvp->v_iflag & VI_DOOMED) { /* forced unmount */ CACHE_RUNLOCK(); - vdrop(*vp); + vfslocked = VFS_LOCK_GIANT(dvp->v_mount); + vrele(dvp); + VFS_UNLOCK_GIANT(vfslocked); error = ENOENT; SDT_PROBE(vfs, namecache, fullpath, return, error, vp, NULL, 0, 0); return (error); } - vdrop(*vp); + /* + * *vp has its use count incremented still. + */ return (0); } @@ -1149,10 +1153,11 @@ static int vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir, char *buf, char **retbuf, u_int buflen) { - int error, slash_prefixed; + int error, slash_prefixed, vfslocked; #ifdef KDTRACE_HOOKS struct vnode *startvp = vp; #endif + struct vnode *vp1; buflen--; buf[buflen] = '\0'; @@ -1161,6 +1166,7 @@ vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir, SDT_PROBE(vfs, namecache, fullpath, entry, vp, 0, 0, 0, 0); numfullpathcalls++; + vref(vp); CACHE_RLOCK(); if (vp->v_type != VDIR) { error = vn_vptocnp_locked(&vp, td->td_ucred, buf, &buflen); @@ -1168,6 +1174,9 @@ vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir, return (error); if (buflen == 0) { CACHE_RUNLOCK(); + vfslocked = VFS_LOCK_GIANT(vp->v_mount); + vrele(vp); + VFS_UNLOCK_GIANT(vfslocked); return (ENOMEM); } buf[--buflen] = '/'; @@ -1177,16 +1186,29 @@ vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir, if (vp->v_vflag & VV_ROOT) { if (vp->v_iflag & VI_DOOMED) { /* forced unmount */ CACHE_RUNLOCK(); + vfslocked = VFS_LOCK_GIANT(vp->v_mount); + vrele(vp); + VFS_UNLOCK_GIANT(vfslocked); error = ENOENT; SDT_PROBE(vfs, namecache, fullpath, return, error, vp, NULL, 0, 0); break; } - vp = vp->v_mount->mnt_vnodecovered; + vp1 = vp->v_mount->mnt_vnodecovered; + vref(vp1); + CACHE_RUNLOCK(); + vfslocked = VFS_LOCK_GIANT(vp->v_mount); + vrele(vp); + VFS_UNLOCK_GIANT(vfslocked); + vp = vp1; + CACHE_RLOCK(); continue; } if (vp->v_type != VDIR) { CACHE_RUNLOCK(); + vfslocked = VFS_LOCK_GIANT(vp->v_mount); + vrele(vp); + VFS_UNLOCK_GIANT(vfslocked); numfullpathfail1++; error = ENOTDIR; SDT_PROBE(vfs, namecache, fullpath, return, @@ -1198,6 +1220,9 @@ vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir, break; if (buflen == 0) { CACHE_RUNLOCK(); + vfslocked = VFS_LOCK_GIANT(vp->v_mount); + vrele(vp); + VFS_UNLOCK_GIANT(vfslocked); error = ENOMEM; SDT_PROBE(vfs, namecache, fullpath, return, error, startvp, NULL, 0, 0); @@ -1211,6 +1236,9 @@ vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir, if (!slash_prefixed) { if (buflen == 0) { CACHE_RUNLOCK(); + vfslocked = VFS_LOCK_GIANT(vp->v_mount); + vrele(vp); + VFS_UNLOCK_GIANT(vfslocked); numfullpathfail4++; SDT_PROBE(vfs, namecache, fullpath, return, ENOMEM, startvp, NULL, 0, 0); @@ -1220,6 +1248,9 @@ vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir, } numfullpathfound++; CACHE_RUNLOCK(); + vfslocked = VFS_LOCK_GIANT(vp->v_mount); + vrele(vp); + VFS_UNLOCK_GIANT(vfslocked); SDT_PROBE(vfs, namecache, fullpath, return, 0, startvp, buf + buflen, 0, 0); diff --git a/sys/kern/vfs_default.c b/sys/kern/vfs_default.c index e9f8151c9919..e47498eeb229 100644 --- a/sys/kern/vfs_default.c +++ b/sys/kern/vfs_default.c @@ -844,7 +844,7 @@ out: free(dirbuf, M_TEMP); if (!error) { *buflen = i; - vhold(*dvp); + vref(*dvp); } if (covered) { vput(*dvp);