[PATCH v2 1/1] NFSD: fix use-after-free in __nfs42_ssc_open()

[Dai Ngo <dai.ngo@xxxxxxxxxx>]

Problem caused by source's vfsmount being unmounted but remains
on the delayed unmount list. This happens when nfs42_ssc_open()
return errors.

Fixed by removing nfsd4_interssc_connect(), leave the vfsmount
for the laundromat to unmount when idle time expires.

Removed unneeded check for NULL nfsd_net and added pr_warn
if vfsmount not found on delayed unmount list.

Reported-by: Xingyuan Mo <hdthky0@xxxxxxxxx>
Signed-off-by: Dai Ngo <dai.ngo@xxxxxxxxxx>
---
 fs/nfsd/nfs4proc.c | 32 ++++++++------------------------
 1 file changed, 8 insertions(+), 24 deletions(-)

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 8beb2bc4c328..84646df60212 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -1463,13 +1463,6 @@ nfsd4_interssc_connect(struct nl4_server *nss, struct svc_rqst *rqstp,
 	return status;
 }
 
-static void
-nfsd4_interssc_disconnect(struct vfsmount *ss_mnt)
-{
-	nfs_do_sb_deactive(ss_mnt->mnt_sb);
-	mntput(ss_mnt);
-}
-
 /*
  * Verify COPY destination stateid.
  *
@@ -1526,10 +1519,6 @@ nfsd4_cleanup_inter_ssc(struct vfsmount *ss_mnt, struct file *filp,
 	nfsd_file_put(dst);
 	fput(filp);
 
-	if (!nn) {
-		mntput(ss_mnt);
-		return;
-	}
 	spin_lock(&nn->nfsd_ssc_lock);
 	timeout = msecs_to_jiffies(nfsd4_ssc_umount_timeout);
 	list_for_each_entry_safe(ni, tmp, &nn->nfsd_ssc_mount_list, nsui_list) {
@@ -1548,10 +1537,8 @@ nfsd4_cleanup_inter_ssc(struct vfsmount *ss_mnt, struct file *filp,
 		}
 	}
 	spin_unlock(&nn->nfsd_ssc_lock);
-	if (!found) {
-		mntput(ss_mnt);
-		return;
-	}
+	if (!found)
+		pr_warn("vfsmount not found on delayed unmount list\n");
 }
 
 #else /* CONFIG_NFSD_V4_2_INTER_SSC */
@@ -1572,11 +1559,6 @@ nfsd4_cleanup_inter_ssc(struct vfsmount *ss_mnt, struct file *filp,
 {
 }
 
-static void
-nfsd4_interssc_disconnect(struct vfsmount *ss_mnt)
-{
-}
-
 static struct file *nfs42_ssc_open(struct vfsmount *ss_mnt,
 				   struct nfs_fh *src_fh,
 				   nfs4_stateid *stateid)
@@ -1762,7 +1744,7 @@ static int nfsd4_do_async_copy(void *data)
 		struct file *filp;
 
 		filp = nfs42_ssc_open(copy->ss_mnt, &copy->c_fh,
-				      &copy->stateid);
+					&copy->stateid);
 		if (IS_ERR(filp)) {
 			switch (PTR_ERR(filp)) {
 			case -EBADF:
@@ -1771,7 +1753,7 @@ static int nfsd4_do_async_copy(void *data)
 			default:
 				nfserr = nfserr_offload_denied;
 			}
-			nfsd4_interssc_disconnect(copy->ss_mnt);
+			/* ss_mnt will be unmounted by the laundromat */
 			goto do_callback;
 		}
 		nfserr = nfsd4_do_copy(copy, filp, copy->nf_dst->nf_file,
@@ -1852,8 +1834,10 @@ nfsd4_copy(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	if (async_copy)
 		cleanup_async_copy(async_copy);
 	status = nfserrno(-ENOMEM);
-	if (nfsd4_ssc_is_inter(copy))
-		nfsd4_interssc_disconnect(copy->ss_mnt);
+	/*
+	 * source's vfsmount of inter-copy will be unmounted
+	 * by the laundromat
+	 */
 	goto out;
 }
 
-- 
2.9.5