Re: [PATCH v3 1/1] NFSD: fix use-after-free in __nfs42_ssc_open()

dai.ngo@xxxxxxxxxx · Mon, 12 Dec 2022 23:00:10 -0800

On 12/12/22 7:38 PM, Xingyuan Mo wrote:
On Tue, Dec 13, 2022 at 6:50 AM Dai Ngo <dai.ngo@xxxxxxxxxx> wrote:
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@xxxxxxxxx>
Signed-off-by: Dai Ngo <dai.ngo@xxxxxxxxxx>
---
  fs/nfsd/nfs4proc.c | 20 +++++---------------
  1 file changed, 5 insertions(+), 15 deletions(-)

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 8beb2bc4c328..b79ee65ae016 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.
   *
@@ -1572,11 +1565,6 @@ 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)
@@ -1771,7 +1759,7 @@ 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 +1840,10 @@ 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

My test results show that this patch can fix the problem.

Thank you Xingyuan for testing the patch.

-Dai


Regards,
Xingyuan Mo






