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netfilter: Can't fail and free after table replacement

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All xtables variants suffer from the defect that the copy_to_user()
to copy the counters to user memory may fail after the table has
already been exchanged and thus exposed. Return an error at this
point will result in freeing the already exposed table. Any
subsequent packet processing will result in a kernel panic.

We can't copy the counters before exposing the new tables as we
want provide the counter state after the old table has been
unhooked. Therefore convert this into a silent error.

Cc: Florian Westphal <fw@strlen.de>
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Thomas Graf 2014-04-04 17:57:45 +02:00 committed by Pablo Neira Ayuso
parent 2fec6bb6f4
commit c58dd2dd44
4 changed files with 14 additions and 9 deletions
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5
net/bridge/netfilter/ebtables.c
View File

@ -1044,10 +1044,9 @@ static int do_replace_finish(struct net *net, struct ebt_replace *repl,
if (repl->num_counters &&
copy_to_user(repl->counters, counterstmp,
repl->num_counters * sizeof(struct ebt_counter))) {
ret = -EFAULT;
/* Silent error, can't fail, new table is already in place */
net_warn_ratelimited("ebtables: counters copy to user failed while replacing table\n");
}
else
ret = 0;
/* decrease module count and free resources */
EBT_ENTRY_ITERATE(table->entries, table->entries_size,

6
net/ipv4/netfilter/arp_tables.c
View File

@ -1044,8 +1044,10 @@ static int __do_replace(struct net *net, const char *name,
xt_free_table_info(oldinfo);
if (copy_to_user(counters_ptr, counters,
sizeof(struct xt_counters) * num_counters) != 0)
ret = -EFAULT;
sizeof(struct xt_counters) * num_counters) != 0) {
/* Silent error, can't fail, new table is already in place */
net_warn_ratelimited("arptables: counters copy to user failed while replacing table\n");
}
vfree(counters);
xt_table_unlock(t);
return ret;

6
net/ipv4/netfilter/ip_tables.c
View File

@ -1231,8 +1231,10 @@ __do_replace(struct net *net, const char *name, unsigned int valid_hooks,
xt_free_table_info(oldinfo);
if (copy_to_user(counters_ptr, counters,
sizeof(struct xt_counters) * num_counters) != 0)
ret = -EFAULT;
sizeof(struct xt_counters) * num_counters) != 0) {
/* Silent error, can't fail, new table is already in place */
net_warn_ratelimited("iptables: counters copy to user failed while replacing table\n");
}
vfree(counters);
xt_table_unlock(t);
return ret;

6
net/ipv6/netfilter/ip6_tables.c
View File

@ -1241,8 +1241,10 @@ __do_replace(struct net *net, const char *name, unsigned int valid_hooks,
xt_free_table_info(oldinfo);
if (copy_to_user(counters_ptr, counters,
sizeof(struct xt_counters) * num_counters) != 0)
ret = -EFAULT;
sizeof(struct xt_counters) * num_counters) != 0) {
/* Silent error, can't fail, new table is already in place */
net_warn_ratelimited("ip6tables: counters copy to user failed while replacing table\n");
}
vfree(counters);
xt_table_unlock(t);
return ret;