From bbc327f73b2afb1d21c138d9e838c671e2378ab8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tomasz=20Mo=C5=84?= <[email protected]>
Date: Sun, 25 Aug 2019 20:28:47 +0200
Subject: [PATCH] NFS: Fix hash table key memory corruption
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When the same (as determined by key_equal_func) key gets added to the
GHashTable, old value gets freed and replaced with the new one. This is
fine for hash tables where the key validity is not tightly coupled to
the actual data.

In the nfs_name_snoop_matched hash table the key becomes invalid once
the value gets destroyed (because it shares the data pointed to by fh,
which gets freed once the value is destroyed).

A problematic capture includes packets such that the matching fh gets
added twice to the nfs_name_snoop_matched hash table. Prior to this
change the hash table would end up in a state where the new value is
associated with the old key (which contains pointer to already freed
memory). According to the nfs_name_snoop_matched_equal(), the old key
was equal to the key intended for new value *at the time* of insertion.

This change fixes the bug by using g_hash_table_replace() which does
update the key in case it already exists in the GHashTable.

Bug: 16017
Bug: 16019
Change-Id: Ib3943f1e27e82c05d9abaa1e436554b37a98488e
Reviewed-on: https://code.wireshark.org/review/34360
Reviewed-by: Michael Mann <[email protected]>
Petri-Dish: Michael Mann <[email protected]>
Tested-by: Petri Dish Buildbot
Reviewed-by: Anders Broman <[email protected]>
(cherry picked from commit efe2926a66d3d7187a260226678daeb2aa6e4832)
Reviewed-on: https://code.wireshark.org/review/34362
Reviewed-by: Tomasz Moń <[email protected]>
---
 epan/dissectors/packet-nfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/epan/dissectors/packet-nfs.c b/epan/dissectors/packet-nfs.c
index 489d61afc5..715ee8294b 100644
--- a/epan/dissectors/packet-nfs.c
+++ b/epan/dissectors/packet-nfs.c
@@ -1196,7 +1196,7 @@ nfs_name_snoop_add_fh(int xid, tvbuff_t *tvb, int fh_offset, int fh_length)
 	key->fh = nns->fh;
 
 	g_hash_table_steal(nfs_name_snoop_unmatched, GINT_TO_POINTER(xid));
-	g_hash_table_insert(nfs_name_snoop_matched, key, nns);
+	g_hash_table_replace(nfs_name_snoop_matched, key, nns);
 }