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Move lockMountpoint to the beginning of pivot_root.

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Reported-by: syzbot+5ec859d679b01a1e4a07@syzkaller.appspotmail.com
Reported-by: syzbot+0ef015d68ad98468ecf0@syzkaller.appspotmail.com
PiperOrigin-RevId: 584344550
This commit is contained in:
Lucas Manning
2023-11-21 09:19:33 -08:00
committed by gVisor bot
parent 2bf4a4e331
commit c16916e7d7
1 changed files with 22 additions and 35 deletions
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pkg/sentry/vfs/mount.go
+22 -35
View File
@@ -1062,16 +1062,24 @@ func (vfs *VirtualFilesystem) PivotRoot(ctx context.Context, creds *auth.Credent
return
}
defer newRoot.DecRef(ctx)
putOld, err := vfs.GetDentryAt(ctx, creds, putOldPop, &GetDentryOptions{CheckSearchable: true})
if err != nil {
return
}
defer putOld.DecRef(ctx)
oldRoot = RootFromContext(ctx)
defer oldRoot.DecRef(ctx)
retry:
epoch := vfs.mounts.seq.BeginRead()
putOldVd, err := vfs.GetDentryAt(ctx, creds, putOldPop, &GetDentryOptions{CheckSearchable: true})
if err != nil {
return
}
vfs.lockMounts()
defer vfs.unlockMounts(ctx)
putOld, err := vfs.lockMountpoint(putOldVd)
if err != nil {
return
}
vfs.delayDecRef(putOld)
cleanup := cleanup.Make(func() { putOld.dentry.mu.Unlock() })
defer cleanup.Clean()
// Neither new_root nor put_old can be on the same mount as the current
// root mount.
if newRoot.mount == oldRoot.mount || putOld.mount == oldRoot.mount {
@@ -1082,8 +1090,7 @@ retry:
return newRoot, oldRoot, linuxerr.EINVAL
}
// put_old must be at or underneath new_root.
path, err := vfs.PathnameReachable(ctx, newRoot, putOld)
if err != nil || len(path) == 0 {
if !vfs.isPathReachable(ctx, newRoot, putOld) {
return newRoot, oldRoot, linuxerr.EINVAL
}
// The current root directory must be a mountpoint
@@ -1091,55 +1098,35 @@ retry:
if oldRoot.mount.root != oldRoot.dentry {
return newRoot, oldRoot, linuxerr.EINVAL
}
// The current root and the new root must be in the context's mount namespace.
ns := MountNamespaceFromContext(ctx)
defer ns.DecRef(ctx)
vfs.lockMounts()
vfs.delayDecRef(ns)
if oldRoot.mount.ns != ns || newRoot.mount.ns != ns {
vfs.unlockMounts(ctx)
return newRoot, oldRoot, linuxerr.EINVAL
}
// The current root and the new root cannot be on the rootfs mount.
if oldRoot.mount.parent() == nil || newRoot.mount.parent() == nil {
vfs.unlockMounts(ctx)
return newRoot, oldRoot, linuxerr.EINVAL
}
// Either the mount point at new_root, or the parent mount of that mount
// point, has propagation type MS_SHARED.
if newRootParent := newRoot.mount.parent(); newRoot.mount.isShared || newRootParent.isShared {
vfs.unlockMounts(ctx)
return newRoot, oldRoot, linuxerr.EINVAL
}
// put_old is a mount point and has the propagation type MS_SHARED.
if putOld.mount.root == putOld.dentry && putOld.mount.isShared {
vfs.unlockMounts(ctx)
return newRoot, oldRoot, linuxerr.EINVAL
}
cleanup.Release()
putOld.IncRef()
putOldMp, err := vfs.lockMountpoint(putOld)
if err != nil {
vfs.delayDecRef(putOldMp)
vfs.unlockMounts(ctx)
return newRoot, oldRoot, err
}
if !vfs.mounts.seq.BeginWriteOk(epoch) {
// Checks above raced with a mount change.
putOldMp.dentry.mu.Unlock()
vfs.unlockMounts(ctx)
goto retry
}
defer vfs.unlockMounts(ctx)
vfs.mounts.seq.BeginWrite()
mp := vfs.disconnectLocked(newRoot.mount)
vfs.delayDecRef(mp)
rootMp := vfs.disconnectLocked(oldRoot.mount)
vfs.connectLocked(oldRoot.mount, putOldMp, ns)
putOldMp.dentry.mu.Unlock()
putOld.IncRef()
vfs.connectLocked(oldRoot.mount, putOld, ns)
putOld.dentry.mu.Unlock()
rootMp.dentry.mu.Lock()
vfs.connectLocked(newRoot.mount, rootMp, ns)