2018-06-20 16:35:33

by Jann Horn

Subject: [PATCH net] 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 <[email protected]>
---
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

2018-06-26 18:17:39

by Pablo Neira Ayuso

Subject: Re: [PATCH net] netfilter: nf_log: fix uninit read in nf_log_proc_dostring

On Wed, Jun 20, 2018 at 06:33:45PM +0200, Jann Horn wrote:
> 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.

Applied, thanks.