[PATCH 5.10 199/406] NFS: Guard against READDIR loop when entry names exceed MAXNAMELEN

Greg Kroah-Hartman
2023-09-17T19:33:46Z

From: Benjamin Coddington <bcodding@redhat.com>

[ Upstream commit f67b55b6588bcf9316a1e6e8d529100a5aa3ebe6 ]

Commit 64cfca85bacd asserts the only valid return values for
nfs2/3_decode_dirent should not include -ENAMETOOLONG, but for a server
that sends a filename3 which exceeds MAXNAMELEN in a READDIR response the
client's behavior will be to endlessly retry the operation.

We could map -ENAMETOOLONG into -EBADCOOKIE, but that would produce
truncated listings without any error. The client should return an error
for this case to clearly assert that the server implementation must be
corrected.

Fixes: 64cfca85bacd ("NFS: Return valid errors from nfs2/3_decode_dirent()")
Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/nfs/nfs2xdr.c | 2 +-
fs/nfs/nfs3xdr.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/nfs2xdr.c b/fs/nfs/nfs2xdr.c
index 5e6453e9b3079..b34196da1f945 100644
--- a/fs/nfs/nfs2xdr.c
+++ b/fs/nfs/nfs2xdr.c
@@ -948,7 +948,7 @@ int nfs2_decode_dirent(struct xdr_stream *xdr, struct nfs_entry *entry,

error = decode_filename_inline(xdr, &entry->name, &entry->len);
if (unlikely(error))
- return -EAGAIN;
+ return error == -ENAMETOOLONG ? -ENAMETOOLONG : -EAGAIN;

/*
* The type (size and byte order) of nfscookie isn't defined in
diff --git a/fs/nfs/nfs3xdr.c b/fs/nfs/nfs3xdr.c
index b5a9379b14504..509f32845d7b2 100644
--- a/fs/nfs/nfs3xdr.c
+++ b/fs/nfs/nfs3xdr.c
@@ -1987,7 +1987,7 @@ int nfs3_decode_dirent(struct xdr_stream *xdr, struct nfs_entry *entry,

error = decode_inline_filename3(xdr, &entry->name, &entry->len);
if (unlikely(error))
- return -EAGAIN;
+ return error == -ENAMETOOLONG ? -ENAMETOOLONG : -EAGAIN;

error = decode_cookie3(xdr, &new_cookie);
if (unlikely(error))
--
2.40.1