[PATCH 5.7 173/204] nfs: Fix getxattr kernel panic and memory overflow

Greg Kroah-Hartman
2020-08-20T09:45:15Z

From: Jeffrey Mitchell <jeffrey.mitchell@starlab.io>

[ Upstream commit b4487b93545214a9db8cbf32e86411677b0cca21 ]

Move the buffer size check to decode_attr_security_label() before memcpy()
Only call memcpy() if the buffer is large enough

Fixes: aa9c2669626c ("NFS: Client implementation of Labeled-NFS")
Signed-off-by: Jeffrey Mitchell <jeffrey.mitchell@starlab.io>
[Trond: clean up duplicate test of label->len != 0]
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/nfs/nfs4proc.c | 2 --
fs/nfs/nfs4xdr.c | 6 +++++-
2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 2e2dac29a9e91..45e0585e0667c 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -5845,8 +5845,6 @@ static int _nfs4_get_security_label(struct inode *inode, void *buf,
return ret;
if (!(fattr.valid & NFS_ATTR_FATTR_V4_SECURITY_LABEL))
return -ENOENT;
- if (buflen < label.len)
- return -ERANGE;
return 0;
}

diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index 47817ef0aadb1..4e0d8a3b89b67 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -4166,7 +4166,11 @@ static int decode_attr_security_label(struct xdr_stream *xdr, uint32_t *bitmap,
return -EIO;
if (len < NFS4_MAXLABELLEN) {
if (label) {
- memcpy(label->label, p, len);
+ if (label->len) {
+ if (label->len < len)
+ return -ERANGE;
+ memcpy(label->label, p, len);
+ }
label->len = len;
label->pi = pi;
label->lfs = lfs;
--
2.25.1