Heinrich Schuchardt писал 2022-06-04 20:44:
On 6/2/22 20:32, gerbert wrote:
This patch tries to fix a CVE-2019-14196 fix
In if-condition, where NFSV2_FLAG is checked, memcpy call is
performed
to transfer a reply data of NFS_FHSIZE size. Since the data field in
struct rpc_t structure has the size of (1024 / 4) + 26 = 282, while
NFS_FHSIZE is only 32, it won't lead to out-of-bounds write
(considering
the size of data array won't change in the future).
What concerns if-condition for NFSV3_FLAG, since filefh3_length is
signed integer, it may carry negative values which may lead to memcpy
failure, so in this case we need to introduce not only boundary check
(filefh3_length > NFS3_FHSIZE), which exists, but also make sure that
filefh3_length is not negative.
Signed-off-by: gerbert <gerb...@users.noreply.github.com>
---
net/nfs.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/net/nfs.c b/net/nfs.c
index 9152ab742e..5186130ea9 100644
--- a/net/nfs.c
+++ b/net/nfs.c
@@ -566,13 +566,13 @@ static int nfs_lookup_reply(uchar *pkt, unsigned
len)
}
if (supported_nfs_versions & NFSV2_FLAG) {
- if (((uchar *)&(rpc_pkt.u.reply.data[0]) - (uchar
*)(&rpc_pkt)
+ NFS_FHSIZE) > len)
- return -NFS_RPC_DROP;
memcpy(filefh, rpc_pkt.u.reply.data + 1, NFS_FHSIZE);
} else { /* NFSV3_FLAG */
filefh3_length = ntohl(rpc_pkt.u.reply.data[1]);
+ if (filefh3_length < 0)
This is the definition:
static unsigned int filefh3_length
The value cannot be negative.
That's right. It's unsigned now. Unfortunately I was looking into the
version
I was using in the project, which is, 2021.01. A bit outdated and has
this field
as signed integer. That's why I was thinking that this should work.
Meanwhile, I then think that this part can be removed:
- if (((uchar *)&(rpc_pkt.u.reply.data[0]) - (uchar
*)(&rpc_pkt)
+ NFS_FHSIZE) > len)
as
memcpy(filefh, rpc_pkt.u.reply.data + 1, NFS_FHSIZE);
won't leave the boundary of 'rpc_pkt.u.reply.data + 1' due to the size
of NFS_FHSIZE.
Cf.
bdbf7a05e26f3c5 ("net: nfs: Fix CVE-2022-30767 (old CVE-2019-14196)")
+ return -NFS_RPC_DROP;
if (filefh3_length > NFS3_FHSIZE)
- filefh3_length = NFS3_FHSIZE;
+ filefh3_length = NFS3_FHSIZE;
This seems to be an unrelated change.
Thought about a little cosmetics here.
Best regards
Heinrich
memcpy(filefh, rpc_pkt.u.reply.data + 2, filefh3_length);
}
Kind regards,
Gerbert
