From: Jann Horn Date: Wed, 20 Jun 2018 16:33:45 +0000 (+0200) Subject: netfilter: nf_log: fix uninit read in nf_log_proc_dostring X-Git-Tag: v4.18-rc4~35^2~34^2~2 X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=dffd22aed2aa1e804bccf19b30a421e89ee2ae61;p=users%2Fjedix%2Flinux-maple.git netfilter: nf_log: fix uninit read in nf_log_proc_dostring 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 --- 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)