[PATCH] nfs: Fix getxattr kernel panic and memory overflow

[Jeffrey Mitchell]

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

Signed-off-by: Jeffrey Mitchell <jeffrey.mitch...@starlab.io>
---
 fs/nfs/nfs4proc.c | 2 --
 fs/nfs/nfs4xdr.c  | 5 ++++-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 2e2dac29a9e9..45e0585e0667 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 47817ef0aadb..50162e0a959c 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -4166,7 +4166,10 @@ 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 && label->len < len)
+                                       return -ERANGE;
+                               if (label->len)
+                                       memcpy(label->label, p, len);
                                label->len = len;
                                label->pi = pi;
                                label->lfs = lfs;
-- 
2.25.1