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Add vnode interlocking to devfs.

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This prevents race conditions that can cause pagefaults or devfs
to use arbitrary vnodes.

MFC after:	1 week
This commit is contained in:
Stephan Uphoff 2006-07-12 20:25:35 +00:00
parent df2f5de4e5
commit 56eeb277cb
1 changed files with 33 additions and 16 deletions
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49
sys/fs/devfs/devfs_vnops.c
View file

@ -72,6 +72,9 @@ static struct fileops devfs_ops_f;
#include <fs/devfs/devfs.h>
#include <fs/devfs/devfs_int.h>
static struct mtx devfs_de_interlock;
MTX_SYSINIT(devfs_de_interlock, &devfs_de_interlock, "devfs interlock", MTX_DEF);
static int
devfs_fp_check(struct file *fp, struct cdev **devp, struct cdevsw **dswp)
{
@ -132,13 +135,18 @@ devfs_allocv(struct devfs_dirent *de, struct mount *mp, struct vnode **vpp, stru
KASSERT(td == curthread, ("devfs_allocv: td != curthread"));
loop:
mtx_lock(&devfs_de_interlock);
vp = de->de_vnode;
if (vp != NULL) {
if (vget(vp, LK_EXCLUSIVE, td))
VI_LOCK(vp);
mtx_unlock(&devfs_de_interlock);
if (vget(vp, LK_EXCLUSIVE | LK_INTERLOCK, td))
goto loop;
*vpp = vp;
return (0);
}
mtx_unlock(&devfs_de_interlock);
if (de->de_dirent->d_type == DT_CHR) {
if (!(de->de_cdp->cdp_flags & CDP_ACTIVE))
return (ENOENT);
@ -171,8 +179,10 @@ loop:
} else {
vp->v_type = VBAD;
}
mtx_lock(&devfs_de_interlock);
vp->v_data = de;
de->de_vnode = vp;
mtx_unlock(&devfs_de_interlock);
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
#ifdef MAC
mac_associate_vnode_devfs(mp, de, vp);
@ -869,11 +879,15 @@ devfs_reclaim(struct vop_reclaim_args *ap)
struct vnode *vp = ap->a_vp;
struct devfs_dirent *de;
struct cdev *dev;
mtx_lock(&devfs_de_interlock);
de = vp->v_data;
if (de != NULL)
if (de != NULL) {
de->de_vnode = NULL;
vp->v_data = NULL;
vp->v_data = NULL;
}
mtx_unlock(&devfs_de_interlock);
vnode_destroy_vobject(vp);
dev = vp->v_rdev;
@ -915,10 +929,6 @@ devfs_remove(struct vop_remove_args *ap)
* is orphaned by setting v_op to deadfs so we need to let go of it
* as well so that we create a new one next time around.
*
* XXX: locking :-(
* XXX: We mess around with other mountpoints without holding their sxlock.
* XXX: We hold the devlock() when we zero their vnode pointer, but is that
* XXX: enough ?
*/
static int
devfs_revoke(struct vop_revoke_args *ap)
@ -934,25 +944,32 @@ devfs_revoke(struct vop_revoke_args *ap)
dev = vp->v_rdev;
cdp = dev->si_priv;
for (;;) {
mtx_lock(&devfs_de_interlock);
dev_lock();
vp2 = NULL;
for (i = 0; i <= cdp->cdp_maxdirent; i++) {
de = cdp->cdp_dirents[i];
if (de == NULL)
continue;
vp2 = de->de_vnode;
de->de_vnode = NULL;
if (vp2 != NULL)
vp2 = de->de_vnode;
if (vp2 != NULL) {
de->de_vnode = NULL;
dev_unlock();
VI_LOCK(vp2);
mtx_unlock(&devfs_de_interlock);
vholdl(vp2);
VI_UNLOCK(vp2);
vgone(vp2);
vdrop(vp2);
break;
}
}
dev_unlock();
if (vp2 != NULL) {
/* XXX */
vhold(vp2);
vgone(vp2);
vdrop(vp2);
continue;
}
dev_unlock();
mtx_unlock(&devfs_de_interlock);
break;
}
return (0);