From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roman Mashak Subject: [PATCH net-next 1/1] net sched actions: fix invalid pointer dereferencing if skbedit flags missing Date: Wed, 9 May 2018 17:18:43 -0400 Message-ID: <1525900723-17625-1-git-send-email-mrv@mojatatu.com> Cc: netdev@vger.kernel.org, kernel@mojatatu.com, jhs@mojatatu.com, xiyou.wangcong@gmail.com, jiri@resnulli.us, alexander.duyck@gmail.com, Roman Mashak To: davem@davemloft.net Return-path: Received: from mail-it0-f65.google.com ([209.85.214.65]:51148 "EHLO mail-it0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935325AbeEIVSz (ORCPT ); Wed, 9 May 2018 17:18:55 -0400 Received: by mail-it0-f65.google.com with SMTP id p3-v6so687047itc.0 for ; Wed, 09 May 2018 14:18:54 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: When application fails to pass flags in netlink TLV for a new skbedit action, the kernel results in the following oops: [ 8.307732] BUG: unable to handle kernel paging request at 0000000000021130 [ 8.309167] PGD 80000000193d1067 P4D 80000000193d1067 PUD 180e0067 PMD 0 [ 8.310595] Oops: 0000 [#1] SMP PTI [ 8.311334] Modules linked in: kvm_intel kvm irqbypass crct10dif_pclmul crc32_pclmul ghash_clmulni_intel pcbc aesni_intel aes_x86_64 crypto_simd cryptd glue_helper serio_raw [ 8.314190] CPU: 1 PID: 397 Comm: tc Not tainted 4.17.0-rc3+ #357 [ 8.315252] RIP: 0010:__tcf_idr_release+0x33/0x140 [ 8.316203] RSP: 0018:ffffa0718038f840 EFLAGS: 00010246 [ 8.317123] RAX: 0000000000000001 RBX: 0000000000021100 RCX: 0000000000000000 [ 8.319831] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000021100 [ 8.321181] RBP: 0000000000000000 R08: 000000000004adf8 R09: 0000000000000122 [ 8.322645] R10: 0000000000000000 R11: ffffffff9e5b01ed R12: 0000000000000000 [ 8.324157] R13: ffffffff9e0d3cc0 R14: 0000000000000000 R15: 0000000000000000 [ 8.325590] FS: 00007f591292e700(0000) GS:ffff8fcf5bc40000(0000) knlGS:0000000000000000 [ 8.327001] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 8.327987] CR2: 0000000000021130 CR3: 00000000180e6004 CR4: 00000000001606a0 [ 8.329289] Call Trace: [ 8.329735] tcf_skbedit_init+0xa7/0xb0 [ 8.330423] tcf_action_init_1+0x362/0x410 [ 8.331139] ? try_to_wake_up+0x44/0x430 [ 8.331817] tcf_action_init+0x103/0x190 [ 8.332511] tc_ctl_action+0x11a/0x220 [ 8.333174] rtnetlink_rcv_msg+0x23d/0x2e0 [ 8.333902] ? _cond_resched+0x16/0x40 [ 8.334569] ? __kmalloc_node_track_caller+0x5b/0x2c0 [ 8.335440] ? rtnl_calcit.isra.31+0xf0/0xf0 [ 8.336178] netlink_rcv_skb+0xdb/0x110 [ 8.336855] netlink_unicast+0x167/0x220 [ 8.337550] netlink_sendmsg+0x2a7/0x390 [ 8.338258] sock_sendmsg+0x30/0x40 [ 8.338865] ___sys_sendmsg+0x2c5/0x2e0 [ 8.339531] ? pagecache_get_page+0x27/0x210 [ 8.340271] ? filemap_fault+0xa2/0x630 [ 8.340943] ? page_add_file_rmap+0x108/0x200 [ 8.341732] ? alloc_set_pte+0x2aa/0x530 [ 8.342573] ? finish_fault+0x4e/0x70 [ 8.343332] ? __handle_mm_fault+0xbc1/0x10d0 [ 8.344337] ? __sys_sendmsg+0x53/0x80 [ 8.345040] __sys_sendmsg+0x53/0x80 [ 8.345678] do_syscall_64+0x4f/0x100 [ 8.346339] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [ 8.347206] RIP: 0033:0x7f591191da67 [ 8.347831] RSP: 002b:00007fff745abd48 EFLAGS: 00000246 ORIG_RAX: 000000000000002e [ 8.349179] RAX: ffffffffffffffda RBX: 00007fff745abe70 RCX: 00007f591191da67 [ 8.350431] RDX: 0000000000000000 RSI: 00007fff745abdc0 RDI: 0000000000000003 [ 8.351659] RBP: 000000005af35251 R08: 0000000000000001 R09: 0000000000000000 [ 8.352922] R10: 00000000000005f1 R11: 0000000000000246 R12: 0000000000000000 [ 8.354183] R13: 00007fff745afed0 R14: 0000000000000001 R15: 00000000006767c0 [ 8.355400] Code: 41 89 d4 53 89 f5 48 89 fb e8 aa 20 fd ff 85 c0 0f 84 ed 00 00 00 48 85 db 0f 84 cf 00 00 00 40 84 ed 0f 85 cd 00 00 00 45 84 e4 <8b> 53 30 74 0d 85 d2 b8 ff ff ff ff 0f 8f b3 00 00 00 8b 43 2c [ 8.358699] RIP: __tcf_idr_release+0x33/0x140 RSP: ffffa0718038f840 [ 8.359770] CR2: 0000000000021130 [ 8.360438] ---[ end trace 60c66be45dfc14f0 ]--- The caller calls action's ->init() and passes pointer to "struct tc_action *a", which later may initialized to point at the existing action, otherwise "struct tc_action *a" is still invalid, and therefore dereferencing it is error. So checking flags should be done as early as possible, before idr lookups. Signed-off-by: Roman Mashak --- net/sched/act_skbedit.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/net/sched/act_skbedit.c b/net/sched/act_skbedit.c index ddf69fc01bdf..6c88037faf51 100644 --- a/net/sched/act_skbedit.c +++ b/net/sched/act_skbedit.c @@ -114,17 +114,15 @@ static int tcf_skbedit_init(struct net *net, struct nlattr *nla, mask = nla_data(tb[TCA_SKBEDIT_MASK]); } + if (!flags) + return -EINVAL; + parm = nla_data(tb[TCA_SKBEDIT_PARMS]); exists = tcf_idr_check(tn, parm->index, a, bind); if (exists && bind) return 0; - if (!flags) { - tcf_idr_release(*a, bind); - return -EINVAL; - } - if (!exists) { ret = tcf_idr_create(tn, parm->index, est, a, &act_skbedit_ops, bind, false); -- 2.7.4