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wireguard: allowedips: don't corrupt stack when detecting overflow 

[ Upstream commit c31b14d86d ]

In case push_rcu() and related functions are buggy, there's a
WARN_ON(len >= 128), which the selftest tries to hit by being tricky. In
case it is hit, we shouldn't corrupt the kernel's stack, though;
otherwise it may be hard to even receive the report that it's buggy. So
conditionalize the stack write based on that WARN_ON()'s return value.

Note that this never *actually* happens anyway. The WARN_ON() in the
first place is bounded by IS_ENABLED(DEBUG), and isn't expected to ever
actually hit. This is just a debugging sanity check.

Additionally, hoist the constant 128 into a named enum,
MAX_ALLOWEDIPS_BITS, so that it's clear why this value is chosen.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/all/CAHk-=wjJZGA6w_DxA+k7Ejbqsq+uGK==koPai3sqdsfJqemvag@mail.gmail.com/
Fixes: e7096c131e ("net: WireGuard secure network tunnel")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Jason A. Donenfeld 2022-08-02 14:56:12 +02:00 committed by Greg Kroah-Hartman
parent 73ccc2b153
commit c36369f7db
2 changed files with 9 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
drivers/net/wireguard/allowedips.c
View File

@ -6,6 +6,8 @@
#include "allowedips.h"
#include "peer.h"
enum { MAX_ALLOWEDIPS_BITS = 128 };
static struct kmem_cache *node_cache;
static void swap_endian(u8 *dst, const u8 *src, u8 bits)
@ -40,7 +42,8 @@ static void push_rcu(struct allowedips_node **stack,
struct allowedips_node __rcu *p, unsigned int *len)
{
if (rcu_access_pointer(p)) {
WARN_ON(IS_ENABLED(DEBUG) && *len >= 128);
if (WARN_ON(IS_ENABLED(DEBUG) && *len >= MAX_ALLOWEDIPS_BITS))
return;
stack[(*len)++] = rcu_dereference_raw(p);
}
}
@ -52,7 +55,7 @@ static void node_free_rcu(struct rcu_head *rcu)
static void root_free_rcu(struct rcu_head *rcu)
{
struct allowedips_node *node, *stack[128] = {
struct allowedips_node *node, *stack[MAX_ALLOWEDIPS_BITS] = {
container_of(rcu, struct allowedips_node, rcu) };
unsigned int len = 1;
@ -65,7 +68,7 @@ static void root_free_rcu(struct rcu_head *rcu)
static void root_remove_peer_lists(struct allowedips_node *root)
{
struct allowedips_node *node, *stack[128] = { root };
struct allowedips_node *node, *stack[MAX_ALLOWEDIPS_BITS] = { root };
unsigned int len = 1;
while (len > 0 && (node = stack[--len])) {

6
drivers/net/wireguard/selftest/allowedips.c
View File

@ -593,10 +593,10 @@ bool __init wg_allowedips_selftest(void)
wg_allowedips_remove_by_peer(&t, a, &mutex);
test_negative(4, a, 192, 168, 0, 1);
/* These will hit the WARN_ON(len >= 128) in free_node if something
* goes wrong.
/* These will hit the WARN_ON(len >= MAX_ALLOWEDIPS_BITS) in free_node
* if something goes wrong.
*/
for (i = 0; i < 128; ++i) {
for (i = 0; i < MAX_ALLOWEDIPS_BITS; ++i) {
part = cpu_to_be64(~(1LLU << (i % 64)));
memset(&ip, 0xff, 16);
memcpy((u8 *)&ip + (i < 64) * 8, &part, 8);