From: Jiri Pirko <jiri@mellanox.com>
Date: Tue, 22 Aug 2017 22:46:49 +0200
Subject: net: sched: fix use after free when tcf_chain_destroy is called
multiple times
Patch-mainline: v4.13
Git-commit: 744a4cf63e528c29840f45811d6fb93fd129b87d
References: bsc#1056787
The goto_chain termination action takes a reference of a chain. In that
case, there is an issue when block_put is called tcf_chain_destroy
directly. The follo-up call of tcf_chain_put by goto_chain action free
works with memory that is already freed. This was caught by kasan:
[ 220.337908] BUG: KASAN: use-after-free in tcf_chain_put+0x1b/0x50
[ 220.344103] Read of size 4 at addr ffff88036d1f2cec by task systemd-journal/261
[ 220.353047] CPU: 0 PID: 261 Comm: systemd-journal Not tainted 4.13.0-rc5jiri+ #54
[ 220.360661] Hardware name: Mellanox Technologies Ltd. Mellanox switch/Mellanox x86 mezzanine board, BIOS 4.6.5 08/02/2016
[ 220.371784] Call Trace:
[ 220.374290] <IRQ>
[ 220.376355] dump_stack+0xd5/0x150
[ 220.391485] print_address_description+0x86/0x410
[ 220.396308] kasan_report+0x181/0x4c0
[ 220.415211] tcf_chain_put+0x1b/0x50
[ 220.418949] free_tcf+0x95/0xc0
So allow tcf_chain_destroy to be called multiple times, free only in
case the reference count drops to 0.
Fixes: 5bc1701881e3 ("net: sched: introduce multichain support for filters")
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
net/sched/cls_api.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -215,9 +215,17 @@ static void tcf_chain_flush(struct tcf_c
static void tcf_chain_destroy(struct tcf_chain *chain)
{
- list_del(&chain->list);
+ /* May be already removed from the list by the previous call. */
+ if (!list_empty(&chain->list))
+ list_del_init(&chain->list);
+
tcf_chain_flush(chain);
- kfree(chain);
+
+ /* There might still be a reference held when we got here from
+ * tcf_block_put. Wait for the user to drop reference before free.
+ */
+ if (!chain->refcnt)
+ kfree(chain);
}
struct tcf_chain *tcf_chain_get(struct tcf_block *block, u32 chain_index,