Re: [PATCH net] netfilter: xt_hashlimit: do not allow empty names

Eric Dumazet [off-list ref] wrote:

On Sun, 2018-01-28 at 07:41 -0800, Eric Dumazet wrote:

quoted

From: Eric Dumazet <edumazet@google.com>

Syzbot reported a WARN() in proc_create_data() [1]

Issue here is that xt_hashlimit does not check that user space provided
an empty table name.

quoted

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <redacted>
---
 net/netfilter/xt_hashlimit.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/netfilter/xt_hashlimit.c b/net/netfilter/xt_hashlimit.c
index 5da8746f7b88ff4c9446f256e542e823a6a561b0..eae732e013df92a364b500645360d4606c283a75 100644
--- a/net/netfilter/xt_hashlimit.c
+++ b/net/netfilter/xt_hashlimit.c

@@ -894,6 +894,8 @@ static int hashlimit_mt_check_common(const struct xt_mtchk_param *par,
 			return -ERANGE;
 	}
 
+	if (!name[0])
+		return -EINVAL;
 	mutex_lock(&hashlimit_mutex);
 	*hinfo = htable_find_get(net, name, par->family);
 	if (*hinfo == NULL) {

I wonder if we should also check if name includes a '/' ?

if (!name[0] || strchr(name, '/'))
    return -EINVAL;

I think there should be a helper for this to reject

- 0 length
- /
- .
- ..

in hashlimit case name is IFNMASIZ so we could even use
dev_valid_name() here.