target/linux/generic/patches-4.1/096-ipv4-off-by-one-in-continuation-handling-in-proc-net.patch

   1 From 25b97c016b26039982daaa2c11d83979f93b71ab Mon Sep 17 00:00:00 2001
   2 From: Andy Whitcroft <apw@canonical.com>
   3 Date: Thu, 13 Aug 2015 20:49:01 +0100
   4 Subject: [PATCH] ipv4: off-by-one in continuation handling in /proc/net/route
   5
   6 When generating /proc/net/route we emit a header followed by a line for
   7 each route.  When a short read is performed we will restart this process
   8 based on the open file descriptor.  When calculating the start point we
   9 fail to take into account that the 0th entry is the header.  This leads
  10 us to skip the first entry when doing a continuation read.
  11
  12 This can be easily seen with the comparison below:
  13
  14   while read l; do echo "$l"; done </proc/net/route >A
  15   cat /proc/net/route >B
  16   diff -bu A B | grep '^[+-]'
  17
  18 On my example machine I have approximatly 10KB of route output.  There we
  19 see the very first non-title element is lost in the while read case,
  20 and an entry around the 8K mark in the cat case:
  21
  22   +wlan0 00000000 02021EAC 0003 0 0 400 00000000 0 0 0
  23   -tun1  00C0AC0A 00000000 0001 0 0 950 00C0FFFF 0 0 0
  24
  25 Fix up the off-by-one when reaquiring position on continuation.
  26
  27 Fixes: 8be33e955cb9 ("fib_trie: Fib walk rcu should take a tnode and key instead of a trie and a leaf")
  28 BugLink: http://bugs.launchpad.net/bugs/1483440
  29 Acked-by: Alexander Duyck <alexander.h.duyck@redhat.com>
  30 Signed-off-by: Andy Whitcroft <apw@canonical.com>
  31 Signed-off-by: David S. Miller <davem@davemloft.net>
  32 ---
  33  net/ipv4/fib_trie.c | 2 +-
  34  1 file changed, 1 insertion(+), 1 deletion(-)
  35
  36 --- a/net/ipv4/fib_trie.c
  37 +++ b/net/ipv4/fib_trie.c
  38 @@ -2457,7 +2457,7 @@ static struct key_vector *fib_route_get_
  39                 key = l->key + 1;
  40                 iter->pos++;
  41
  42 -               if (pos-- <= 0)
  43 +               if (--pos <= 0)
  44                         break;
  45
  46                 l = NULL;