Revert "netfilter: x_tables: ensure last rule in base chain matches underflow/policy"

This reverts commit 0d7df906a0e78079a02108b06d32c3ef2238ad25.

Valdis Kletnieks reported that xtables is broken in linux-next since
0d7df906a0e78  ("netfilter: x_tables: ensure last rule in base chain
matches underflow/policy"), as kernel rejects the (well-formed) ruleset:

[   64.402790] ip6_tables: last base chain position 1136 doesn't match underflow 1344 (hook 1)

mark_source_chains is not the correct place for such a check, as it
terminates evaluation of a chain once it sees an unconditional verdict
(following rules are known to be unreachable). It seems preferrable to
fix libiptc instead, so remove this check again.

Fixes: 0d7df906a0e78 ("netfilter: x_tables: ensure last rule in base chain matches underflow/policy")
Reported-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

3 files changed, 3 insertions, 48 deletions

diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index f366ff1cfc19..aaafdbd15ad3 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -309,13 +309,10 @@ static int mark_source_chains(const struct xt_table_info *newinfo,
         for (hook = 0; hook < NF_ARP_NUMHOOKS; hook++) {
                 unsigned int pos = newinfo->hook_entry[hook];
                 struct arpt_entry *e = entry0 + pos;
-                unsigned int last_pos, depth;
 
                 if (!(valid_hooks & (1 << hook)))
                         continue;
 
-                depth = 0;
-                last_pos = pos;
                 /* Set initial back pointer. */
                 e->counters.pcnt = pos;
 
@@ -346,8 +343,6 @@ static int mark_source_chains(const struct xt_table_info *newinfo,
                                         pos = e->counters.pcnt;
                                         e->counters.pcnt = 0;
 
-                                        if (depth)
-                                                --depth;
                                         /* We're at the start. */
                                         if (pos == oldpos)
                                                 goto next;
@@ -372,9 +367,6 @@ static int mark_source_chains(const struct xt_table_info *newinfo,
                                         if (!xt_find_jump_offset(offsets, newpos,
                                                                  newinfo->number))
                                                 return 0;
-
-                                        if (entry0 + newpos != arpt_next_entry(e))
-                                                ++depth;
                                 } else {
                                         /* ... this is a fallthru */
                                         newpos = pos + e->next_offset;
@@ -385,15 +377,8 @@ static int mark_source_chains(const struct xt_table_info *newinfo,
                                 e->counters.pcnt = pos;
                                 pos = newpos;
                         }
-                        if (depth == 0)
-                                last_pos = pos;
-                }
-next:
-                if (last_pos != newinfo->underflow[hook]) {
-                        pr_err_ratelimited("last base chain position %u doesn't match underflow %u (hook %u)\n",
-                                           last_pos, newinfo->underflow[hook], hook);
-                        return 0;
                 }
+next:           ;
         }
         return 1;
 }
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 2362ca2c9e0c..f9063513f9d1 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -378,13 +378,10 @@ mark_source_chains(const struct xt_table_info *newinfo,
         for (hook = 0; hook < NF_INET_NUMHOOKS; hook++) {
                 unsigned int pos = newinfo->hook_entry[hook];
                 struct ipt_entry *e = entry0 + pos;
-                unsigned int last_pos, depth;
 
                 if (!(valid_hooks & (1 << hook)))
                         continue;
 
-                depth = 0;
-                last_pos = pos;
                 /* Set initial back pointer. */
                 e->counters.pcnt = pos;
 
@@ -413,8 +410,6 @@ mark_source_chains(const struct xt_table_info *newinfo,
                                         pos = e->counters.pcnt;
                                         e->counters.pcnt = 0;
 
-                                        if (depth)
-                                                --depth;
                                         /* We're at the start. */
                                         if (pos == oldpos)
                                                 goto next;
@@ -439,9 +434,6 @@ mark_source_chains(const struct xt_table_info *newinfo,
                                         if (!xt_find_jump_offset(offsets, newpos,
                                                                  newinfo->number))
                                                 return 0;
-
-                                        if (entry0 + newpos != ipt_next_entry(e))
-                                                ++depth;
                                 } else {
                                         /* ... this is a fallthru */
                                         newpos = pos + e->next_offset;
@@ -452,15 +444,8 @@ mark_source_chains(const struct xt_table_info *newinfo,
                                 e->counters.pcnt = pos;
                                 pos = newpos;
                         }
-                        if (depth == 0)
-                                last_pos = pos;
-                }
-next:
-                if (last_pos != newinfo->underflow[hook]) {
-                        pr_err_ratelimited("last base chain position %u doesn't match underflow %u (hook %u)\n",
-                                           last_pos, newinfo->underflow[hook], hook);
-                        return 0;
                 }
+next:           ;
         }
         return 1;
 }
diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index 004508753abc..3c36a4c77f29 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -396,13 +396,10 @@ mark_source_chains(const struct xt_table_info *newinfo,
         for (hook = 0; hook < NF_INET_NUMHOOKS; hook++) {
                 unsigned int pos = newinfo->hook_entry[hook];
                 struct ip6t_entry *e = entry0 + pos;
-                unsigned int last_pos, depth;
 
                 if (!(valid_hooks & (1 << hook)))
                         continue;
 
-                depth = 0;
-                last_pos = pos;
                 /* Set initial back pointer. */
                 e->counters.pcnt = pos;
 
@@ -431,8 +428,6 @@ mark_source_chains(const struct xt_table_info *newinfo,
                                         pos = e->counters.pcnt;
                                         e->counters.pcnt = 0;
 
-                                        if (depth)
-                                                --depth;
                                         /* We're at the start. */
                                         if (pos == oldpos)
                                                 goto next;
@@ -457,9 +452,6 @@ mark_source_chains(const struct xt_table_info *newinfo,
                                         if (!xt_find_jump_offset(offsets, newpos,
                                                                  newinfo->number))
                                                 return 0;
-
-                                        if (entry0 + newpos != ip6t_next_entry(e))
-                                                ++depth;
                                 } else {
                                         /* ... this is a fallthru */
                                         newpos = pos + e->next_offset;
@@ -470,15 +462,8 @@ mark_source_chains(const struct xt_table_info *newinfo,
                                 e->counters.pcnt = pos;
                                 pos = newpos;
                         }
-                        if (depth == 0)
-                                last_pos = pos;
-                }
-next:
-                if (last_pos != newinfo->underflow[hook]) {
-                        pr_err_ratelimited("last base chain position %u doesn't match underflow %u (hook %u)\n",
-                                           last_pos, newinfo->underflow[hook], hook);
-                        return 0;
                 }
+next:           ;
         }
         return 1;
 }