releases/4.4.140/netfilter-nf_log-don-t-hold-nf_log_mutex-during-user-access.patch

   1 From ce00bf07cc95a57cd20b208e02b3c2604e532ae8 Mon Sep 17 00:00:00 2001
   2 From: Jann Horn <jannh@google.com>
   3 Date: Mon, 25 Jun 2018 17:22:00 +0200
   4 Subject: netfilter: nf_log: don't hold nf_log_mutex during user access
   5
   6 From: Jann Horn <jannh@google.com>
   7
   8 commit ce00bf07cc95a57cd20b208e02b3c2604e532ae8 upstream.
   9
  10 The old code would indefinitely block other users of nf_log_mutex if
  11 a userspace access in proc_dostring() blocked e.g. due to a userfaultfd
  12 region. Fix it by moving proc_dostring() out of the locked region.
  13
  14 This is a followup to commit 266d07cb1c9a ("netfilter: nf_log: fix
  15 sleeping function called from invalid context"), which changed this code
  16 from using rcu_read_lock() to taking nf_log_mutex.
  17
  18 Fixes: 266d07cb1c9a ("netfilter: nf_log: fix sleeping function calle[...]")
  19 Signed-off-by: Jann Horn <jannh@google.com>
  20 Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
  21 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  22
  23 ---
  24  net/netfilter/nf_log.c |    9 ++++++---
  25  1 file changed, 6 insertions(+), 3 deletions(-)
  26
  27 --- a/net/netfilter/nf_log.c
  28 +++ b/net/netfilter/nf_log.c
  29 @@ -422,14 +422,17 @@ static int nf_log_proc_dostring(struct c
  30                 rcu_assign_pointer(net->nf.nf_loggers[tindex], logger);
  31                 mutex_unlock(&nf_log_mutex);
  32         } else {
  33 +               struct ctl_table tmp = *table;
  34 +
  35 +               tmp.data = buf;
  36                 mutex_lock(&nf_log_mutex);
  37                 logger = nft_log_dereference(net->nf.nf_loggers[tindex]);
  38                 if (!logger)
  39 -                       table->data = "NONE";
  40 +                       strlcpy(buf, "NONE", sizeof(buf));
  41                 else
  42 -                       table->data = logger->name;
  43 -               r = proc_dostring(table, write, buffer, lenp, ppos);
  44 +                       strlcpy(buf, logger->name, sizeof(buf));
  45                 mutex_unlock(&nf_log_mutex);
  46 +               r = proc_dostring(&tmp, write, buffer, lenp, ppos);
  47         }
  48
  49         return r;