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

Dai Ngo
2022-12-11T19:22:59Z

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.

Reported-by: Xingyuan Mo <hdthky0@gmail.com>
Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
---
fs/nfsd/nfs4proc.c | 23 +++++++----------------
1 file changed, 7 insertions(+), 16 deletions(-)

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 8beb2bc4c328..756e42cf0d01 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)
@@ -1762,7 +1750,8 @@ 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 +1760,7 @@ 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 +1841,10 @@ 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