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[PATCH 4.4 12/37] fib_trie: Correct /proc/net/route off by one error

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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Alexander Duyck <alexander.h.duyck@intel.com>


[ Upstream commit fd0285a39b1cb496f60210a9a00ad33a815603e7 ]

The display of /proc/net/route has had a couple issues due to the fact that
when I originally rewrote most of fib_trie I made it so that the iterator
was tracking the next value to use instead of the current.

In addition it had an off by 1 error where I was tracking the first piece
of data as position 0, even though in reality that belonged to the
SEQ_START_TOKEN.

This patch updates the code so the iterator tracks the last reported
position and key instead of the next expected position and key.  In
addition it shifts things so that all of the leaves start at 1 instead of
trying to report leaves starting with offset 0 as being valid.  With these
two issues addressed this should resolve any off by one errors that were
present in the display of /proc/net/route.

Fixes: 25b97c016b26 ("ipv4: off-by-one in continuation handling in /proc/net/route")
Cc: Andy Whitcroft <apw@canonical.com>
Reported-by: Jason Baron <jbaron@akamai.com>
Tested-by: Jason Baron <jbaron@akamai.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv4/fib_trie.c |   21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -2456,22 +2456,19 @@ static struct key_vector *fib_route_get_
 	struct key_vector *l, **tp = &iter->tnode;
 	t_key key;
 
-	/* use cache location of next-to-find key */
+	/* use cached location of previously found key */
 	if (iter->pos > 0 && pos >= iter->pos) {
-		pos -= iter->pos;
 		key = iter->key;
 	} else {
-		iter->pos = 0;
+		iter->pos = 1;
 		key = 0;
 	}
 
-	while ((l = leaf_walk_rcu(tp, key)) != NULL) {
+	pos -= iter->pos;
+
+	while ((l = leaf_walk_rcu(tp, key)) && (pos-- > 0)) {
 		key = l->key + 1;
 		iter->pos++;
-
-		if (--pos <= 0)
-			break;
-
 		l = NULL;
 
 		/* handle unlikely case of a key wrap */
@@ -2480,7 +2477,7 @@ static struct key_vector *fib_route_get_
 	}
 
 	if (l)
-		iter->key = key;	/* remember it */
+		iter->key = l->key;	/* remember it */
 	else
 		iter->pos = 0;		/* forget it */
 
@@ -2508,7 +2505,7 @@ static void *fib_route_seq_start(struct
 		return fib_route_get_idx(iter, *pos);
 
 	iter->pos = 0;
-	iter->key = 0;
+	iter->key = KEY_MAX;
 
 	return SEQ_START_TOKEN;
 }
@@ -2517,7 +2514,7 @@ static void *fib_route_seq_next(struct s
 {
 	struct fib_route_iter *iter = seq->private;
 	struct key_vector *l = NULL;
-	t_key key = iter->key;
+	t_key key = iter->key + 1;
 
 	++*pos;
 
@@ -2526,7 +2523,7 @@ static void *fib_route_seq_next(struct s
 		l = leaf_walk_rcu(&iter->tnode, key);
 
 	if (l) {
-		iter->key = l->key + 1;
+		iter->key = l->key;
 		iter->pos++;
 	} else {
 		iter->pos = 0;

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[PATCH 4.4 00/37] 4.4.34-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 31/37] sparc64: Convert U1copy_{from,to}_user to accurate exception reporting. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 02/37] net: clear sk_err_soft in sk_clone_lock() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 12/37] fib_trie: Correct /proc/net/route off by one error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 27/37] sparc64: Delete __ret_efault. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 25/37] sparc64: Fix illegal relative branches in hypervisor patched TLB cross-call code. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 10/37] ipv6: dccp: add missing bind_conflict to dccp_ipv6_mapped Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 32/37] sparc64: Convert NG4copy_{from,to}_user to accurate exception reporting. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 24/37] sparc64: Fix instruction count in comment for __hypervisor_flush_tlb_pending. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 07/37] dccp: do not send reset to already closed sockets Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 14/37] net: __skb_flow_dissect() must cap its return value Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 30/37] sparc64: Convert GENcopy_{from,to}_user to accurate exception reporting. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 05/37] ip6_tunnel: Clear IP6CB in ip6tunnel_xmit() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 35/37] sparc64: Convert U3copy_{from,to}_user to accurate exception reporting. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 33/37] sparc64: Convert NGcopy_{from,to}_user to accurate exception reporting. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 11/37] sctp: assign assoc_id earlier in __sctp_connect Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 19/37] sparc: serial: sunhv: fix a double lock bug Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 16/37] tcp: take care of truncations done by sk_filter() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 23/37] sparc64: Fix illegal relative branches in hypervisor patched TLB code. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:30 +0100
  [PATCH 4.4 36/37] sparc64: Delete now unused user copy assembler helpers. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:40 +0100
  [PATCH 4.4 09/37] ipv6: dccp: fix out of bound access in dccp_v6_err() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:40 +0100
  [PATCH 4.4 17/37] tty: Prevent ldisc drivers from re-using stale tty fields Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:40 +0100
  [PATCH 4.4 26/37] sparc64: Handle extremely large kernel TLB range flushes more gracefully. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:40 +0100
  [PATCH 4.4 29/37] sparc64: Convert copy_in_user to accurate exception reporting. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:40 +0100
  [PATCH 4.4 34/37] sparc64: Convert NG2copy_{from,to}_user to accurate exception reporting. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:40 +0100
  [PATCH 4.4 15/37] ipv4: use new_gw for redirect neigh lookup Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:40 +0100
  [PATCH 4.4 37/37] sparc64: Delete now unused user copy fixup functions. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:40 +0100
  [PATCH 4.4 01/37] dctcp: avoid bogus doubling of cwnd after loss Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:50 +0100
  [PATCH 4.4 20/37] sparc64 mm: Fix base TSB sizing when hugetlb pages are used Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:50 +0100
  [PATCH 4.4 04/37] bgmac: stop clearing DMA receive control register right after it is set Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:50 +0100
  [PATCH 4.4 21/37] sparc: Handle negative offsets in arch_jump_label_transform Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:50 +0100
  [PATCH 4.4 08/37] dccp: fix out of bound access in dccp_v4_err() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:50 +0100
  [PATCH 4.4 22/37] sparc64: Handle extremely large kernel TSB range flushes sanely. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-19 10:50 +0100
  Re: [PATCH 4.4 00/37] 4.4.34-stable review Guenter Roeck <linux@roeck-us.net> - 2016-11-19 17:30 +0100
  Re: [PATCH 4.4 00/37] 4.4.34-stable review Shuah Khan <shuah.kh@samsung.com> - 2016-11-21 17:40 +0100
    Re: [PATCH 4.4 00/37] 4.4.34-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-21 17:50 +0100

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