NFSD: fix use-after-free in __nfs42_ssc_open()

[ Upstream commit 75333d48f92256a0dec91dbf07835e804fc411c0 ]

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.

We don't need to call nfs_do_sb_deactive when nfs42_ssc_open
return errors since the file was not opened so nfs_server->active
was not incremented. Same as in nfsd4_copy, if we fail to
launch nfsd4_do_async_copy thread then there's no need to
call nfs_do_sb_deactive

Reported-by: Xingyuan Mo <hdthky0@gmail.com>
Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
Tested-by: Xingyuan Mo <hdthky0@gmail.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 32fe7cb..34d1cd5 100644 (file)
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -1465,13 +1465,6 @@ out_err:
        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.
  *
@@ -1574,11 +1567,6 @@ 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)
@@ -1774,7 +1762,7 @@ 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,
@@ -1855,8 +1843,10 @@ out_err:
        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;
 }