[PATCH 6.1 0424/1146] NFSv4.2: Fix a memory stomp in decode_attr_security_label

Greg Kroah-Hartman
2022-12-28T15:54:19Z

From: Trond Myklebust <trond.myklebust@hammerspace.com>

[ Upstream commit 43c1031f7110967c240cb6e922adcfc4b8899183 ]

We must not change the value of label->len if it is zero, since that
indicates we stored a label.

Fixes: b4487b935452 ("nfs: Fix getxattr kernel panic and memory overflow")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/nfs/nfs4xdr.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index 9103e022376a..deec76cf5afe 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -4236,12 +4236,10 @@ static int decode_attr_security_label(struct xdr_stream *xdr, uint32_t *bitmap,
return -EIO;
bitmap[2] &= ~FATTR4_WORD2_SECURITY_LABEL;
if (len < NFS4_MAXLABELLEN) {
- if (label) {
- if (label->len) {
- if (label->len < len)
- return -ERANGE;
- memcpy(label->label, p, len);
- }
+ if (label && label->len) {
+ if (label->len < len)
+ return -ERANGE;
+ memcpy(label->label, p, len);
label->len = len;
label->pi = pi;
label->lfs = lfs;
--
2.35.1