[PATCH AUTOSEL for 4.14 142/161] nfsd: return RESOURCE not GARBAGE_ARGS on too many ops

Sasha Levin
2018-04-09T02:54:07Z

From: "J. Bruce Fields" <bfields@redhat.com>

[ Upstream commit 0078117c6d9160031b866cfa1853514d4f6865d2 ]

A client that sends more than a hundred ops in a single compound
currently gets an rpc-level GARBAGE_ARGS error.

It would be more helpful to return NFS4ERR_RESOURCE, since that gives
the client a better idea how to recover (for example by splitting up the
compound into smaller compounds).

This is all a bit academic since we've never actually seen a reason for
clients to send such long compounds, but we may as well fix it.

While we're there, just use NFSD4_MAX_OPS_PER_COMPOUND == 16, the
constant we already use in the 4.1 case, instead of hard-coding 100.
Chances anyone actually uses even 16 ops per compound are small enough
that I think there's a neglible risk or any regression.

This fixes pynfs test COMP6.

Reported-by: "Lu, Xinyu" <luxy.fnst@cn.fujitsu.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
fs/nfsd/nfs4proc.c | 3 +++
fs/nfsd/nfs4xdr.c | 9 +++++++--
2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 8ce60986fb75..8706b141e4a4 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -1712,6 +1712,9 @@ nfsd4_proc_compound(struct svc_rqst *rqstp)
status = nfserr_minor_vers_mismatch;
if (nfsd_minorversion(args->minorversion, NFSD_TEST) <= 0)
goto out;
+ status = nfserr_resource;
+ if (args->opcnt > NFSD_MAX_OPS_PER_COMPOUND)
+ goto out;

status = nfs41_check_op_ordering(args);
if (status) {
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 2c61c6b8ae09..5dcd7cb45b2d 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -1918,8 +1918,13 @@ nfsd4_decode_compound(struct nfsd4_compoundargs *argp)

if (argp->taglen > NFSD4_MAX_TAGLEN)
goto xdr_error;
- if (argp->opcnt > 100)
- goto xdr_error;
+ /*
+ * NFS4ERR_RESOURCE is a more helpful error than GARBAGE_ARGS
+ * here, so we return success at the xdr level so that
+ * nfsd4_proc can handle this is an NFS-level error.
+ */
+ if (argp->opcnt > NFSD_MAX_OPS_PER_COMPOUND)
+ return 0;

if (argp->opcnt > ARRAY_SIZE(argp->iops)) {
argp->ops = kzalloc(argp->opcnt * sizeof(*argp->ops), GFP_KERNEL);
--
2.15.1