From 4c3b0ae79f0736993c444980c40ebf7a103b6f39 Mon Sep 17 00:00:00 2001 From: Jann Horn Date: Wed, 20 Jun 2018 18:33:45 +0200 Subject: [PATCH] netfilter: nf_log: fix uninit read in nf_log_proc_dostring [ Upstream commit dffd22aed2aa1e804bccf19b30a421e89ee2ae61 ] 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 Signed-off-by: Pablo Neira Ayuso Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- 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 276324abfa60..cdc744aa5889 100644 --- a/net/netfilter/nf_log.c +++ b/net/netfilter/nf_log.c @@ -440,6 +440,10 @@ 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)