From: Gao Feng <gfree.wind@xxxxxxxxxxx>
The helper and timeout strings are from user-space, we need to make
sure they are null terminated. If not, evil user could make kernel
read the unexpected memory, even print it when fail to find by the
following codes.
pr_info_ratelimited("No such helper \"%s\"\n", helper_name);
Signed-off-by: Gao Feng <gfree.wind@xxxxxxxxxxx>
---
v2: reject the non-null terminated string directly, per Pablo
v1: initial version
net/netfilter/xt_CT.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/net/netfilter/xt_CT.c b/net/netfilter/xt_CT.c
index 8790190..03b9a50 100644
--- a/net/netfilter/xt_CT.c
+++ b/net/netfilter/xt_CT.c
@@ -245,12 +245,22 @@ static int xt_ct_tg_check(const struct xt_tgchk_param *par,
}
if (info->helper[0]) {
+ if (strnlen(info->helper, sizeof(info->helper)) == sizeof(info->helper)) {
+ ret = -ENAMETOOLONG;
+ goto err3;
+ }
+
ret = xt_ct_set_helper(ct, info->helper, par);
if (ret < 0)
goto err3;
}
if (info->timeout[0]) {
+ if (strnlen(info->timeout, sizeof(info->timeout)) == sizeof(info->timeout)) {
+ ret = -ENAMETOOLONG;
+ goto err4;
+ }
+
ret = xt_ct_set_timeout(ct, par, info->timeout);
if (ret < 0)
goto err4;
--
1.9.1
--
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