net: nfs: Fix CVE-2022-30767 (old CVE-2019-14196)
This patch mitigates the vulnerability identified via CVE-2019-14196.
The previous patch was bypassed/ineffective, and now the vulnerability
is identified via CVE-2022-30767. The patch removes the sanity check
introduced to mitigate CVE-2019-14196 since it's ineffective.
filefh3_length is changed to unsigned type integer, preventing negative
numbers from being used during comparison with positive values during
size sanity checks.
Signed-off-by: Andrea zi0Black Cappa <zi0Black@protonmail.com>
diff --git a/net/nfs.c b/net/nfs.c
index 3c01ceb..9152ab7 100644
--- a/net/nfs.c
+++ b/net/nfs.c
@@ -52,7 +52,7 @@
static char dirfh[NFS_FHSIZE]; /* NFSv2 / NFSv3 file handle of directory */
static char filefh[NFS3_FHSIZE]; /* NFSv2 / NFSv3 file handle */
-static int filefh3_length; /* (variable) length of filefh when NFSv3 */
+static unsigned int filefh3_length; /* (variable) length of filefh when NFSv3 */
static enum net_loop_state nfs_download_state;
static struct in_addr nfs_server_ip;
@@ -573,8 +573,6 @@
filefh3_length = ntohl(rpc_pkt.u.reply.data[1]);
if (filefh3_length > NFS3_FHSIZE)
filefh3_length = NFS3_FHSIZE;
- if (((uchar *)&(rpc_pkt.u.reply.data[0]) - (uchar *)(&rpc_pkt) + filefh3_length) > len)
- return -NFS_RPC_DROP;
memcpy(filefh, rpc_pkt.u.reply.data + 2, filefh3_length);
}