From 3e18948f17148e6a3c4255bdeaaf01ef6081ceeb Mon Sep 17 00:00:00 2001 From: Thomas Haller Date: Mon, 6 Feb 2017 22:23:52 +0100 Subject: [PATCH] lib: check for integer-overflow in nlmsg_reserve() In general, libnl functions are not robust against calling with invalid arguments. Thus, never call libnl functions with invalid arguments. In case of nlmsg_reserve() this means never provide a @len argument that causes overflow. Still, add an additional safeguard to avoid exploiting such bugs. Assume that @pad is a trusted, small integer. Assume that n->nm_size is a valid number of allocated bytes (and thus much smaller then SIZE_T_MAX). Assume, that @len may be set to an untrusted value. Then the patch avoids an integer overflow resulting in reserving too few bytes. --- lib/msg.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/lib/msg.c b/lib/msg.c index 9af3f3a0f..3e27d4e0b 100644 --- a/lib/msg.c +++ b/lib/msg.c @@ -411,6 +411,9 @@ void *nlmsg_reserve(struct nl_msg *n, size_t len, int pad) size_t nlmsg_len = n->nm_nlh->nlmsg_len; size_t tlen; + if (len > n->nm_size) + return NULL; + tlen = pad ? ((len + (pad - 1)) & ~(pad - 1)) : len; if ((tlen + nlmsg_len) > n->nm_size)