Patch "NFSD: fix use-after-free in __nfs42_ssc_open()" has been added to the 6.1-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

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

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     nfsd-fix-use-after-free-in-__nfs42_ssc_open.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit efbd664f44d31c5f8363b6709bd0f7612366be71
Author: Dai Ngo <dai.ngo@xxxxxxxxxx>
Date:   Mon Dec 12 14:50:11 2022 -0800

    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@xxxxxxxxx>
    Signed-off-by: Dai Ngo <dai.ngo@xxxxxxxxxx>
    Tested-by: Xingyuan Mo <hdthky0@xxxxxxxxx>
    Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 32fe7cbfb28b..34d1cd5883fb 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -1465,13 +1465,6 @@ 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.
  *
@@ -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 @@ 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;
 }