From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jann Horn Subject: [PATCH net] netfilter: nf_log: fix uninit read in nf_log_proc_dostring Date: Wed, 20 Jun 2018 18:33:45 +0200 Message-ID: <20180620163345.212776-1-jannh@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Cc: "David S. Miller" , netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: Pablo Neira Ayuso , Jozsef Kadlecsik , Florian Westphal , netfilter-devel@vger.kernel.org, coreteam@netfilter.org, jannh@google.com Return-path: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org When proc_dostring() is called with a non-zero offset in strict mode, it doesn't just write to the ->data buffer, it also reads. Make sure it doesn't read uninitialized data. Fixes: c6ac37d8d884 ("netfilter: nf_log: fix error on write NONE to [...]") Signed-off-by: Jann Horn --- net/netfilter/nf_log.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/netfilter/nf_log.c b/net/netfilter/nf_log.c index 426457047578..2c47f9ec3511 100644 --- a/net/netfilter/nf_log.c +++ b/net/netfilter/nf_log.c @@ -424,6 +424,10 @@ static int nf_log_proc_dostring(struct ctl_table *table, int write, if (write) { struct ctl_table tmp = *table; + /* proc_dostring() can append to existing strings, so we need to + * initialize it as an empty string. + */ + buf[0] = '\0'; tmp.data = buf; r = proc_dostring(&tmp, write, buffer, lenp, ppos); if (r) -- 2.18.0.rc1.244.gcf134e6275-goog