[PATCH 3.16 133/136] net/sched: act_pedit: fix WARN() in the traffic path

Ben Hutchings
2019-12-17T00:54:26Z

From: Davide Caratti <dcaratti@redhat.com>

commit f67169fef8dbcc1ac6a6a109ecaad0d3b259002c upstream.

when configuring act_pedit rules, the number of keys is validated only on
addition of a new entry. This is not sufficient to avoid hitting a WARN()
in the traffic path: for example, it is possible to replace a valid entry
with a new one having 0 extended keys, thus causing splats in dmesg like:

pedit BUG: index 42
WARNING: CPU: 2 PID: 4054 at net/sched/act_pedit.c:410 tcf_pedit_act+0xc84/0x1200 [act_pedit]
[...]
RIP: 0010:tcf_pedit_act+0xc84/0x1200 [act_pedit]
Code: 89 fa 48 c1 ea 03 0f b6 04 02 84 c0 74 08 3c 03 0f 8e ac 00 00 00 48 8b 44 24 10 48 c7 c7 a0 c4 e4 c0 8b 70 18 e8 1c 30 95 ea <0f> 0b e9 a0 fa ff ff e8 00 03 f5 ea e9 14 f4 ff ff 48 89 58 40 e9
RSP: 0018:ffff888077c9f320 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffffac2983a2
RDX: 0000000000000001 RSI: 0000000000000008 RDI: ffff888053927bec
RBP: dffffc0000000000 R08: ffffed100a726209 R09: ffffed100a726209
R10: 0000000000000001 R11: ffffed100a726208 R12: ffff88804beea780
R13: ffff888079a77400 R14: ffff88804beea780 R15: ffff888027ab2000
FS: 00007fdeec9bd740(0000) GS:ffff888053900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffdb3dfd000 CR3: 000000004adb4006 CR4: 00000000001606e0
Call Trace:
tcf_action_exec+0x105/0x3f0
tcf_classify+0xf2/0x410
__dev_queue_xmit+0xcbf/0x2ae0
ip_finish_output2+0x711/0x1fb0
ip_output+0x1bf/0x4b0
ip_send_skb+0x37/0xa0
raw_sendmsg+0x180c/0x2430
sock_sendmsg+0xdb/0x110
__sys_sendto+0x257/0x2b0
__x64_sys_sendto+0xdd/0x1b0
do_syscall_64+0xa5/0x4e0
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7fdeeb72e993
Code: 48 8b 0d e0 74 2c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d 0d d6 2c 00 00 75 13 49 89 ca b8 2c 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 34 c3 48 83 ec 08 e8 4b cc 00 00 48 89 04 24
RSP: 002b:00007ffdb3de8a18 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 000055c81972b700 RCX: 00007fdeeb72e993
RDX: 0000000000000040 RSI: 000055c81972b700 RDI: 0000000000000003
RBP: 00007ffdb3dea130 R08: 000055c819728510 R09: 0000000000000010
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000040
R13: 000055c81972b6c0 R14: 000055c81972969c R15: 0000000000000080

Fix this moving the check on 'nkeys' earlier in tcf_pedit_init(), so that
attempts to install rules having 0 keys are always rejected with -EINVAL.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.16:
- Drop change in tcf_pedit_keys_ex_parse()
- netlink doesn't support error messages
- Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
--- a/net/sched/act_pedit.c
+++ b/net/sched/act_pedit.c
@@ -50,13 +50,13 @@ static int tcf_pedit_init(struct net *ne
if (tb[TCA_PEDIT_PARMS] == NULL)
return -EINVAL;
parm = nla_data(tb[TCA_PEDIT_PARMS]);
+ if (!parm->nkeys)
+ return -EINVAL;
ksize = parm->nkeys * sizeof(struct tc_pedit_key);
if (nla_len(tb[TCA_PEDIT_PARMS]) < sizeof(*parm) + ksize)
return -EINVAL;

if (!tcf_hash_check(parm->index, a, bind)) {
- if (!parm->nkeys)
- return -EINVAL;
ret = tcf_hash_create(parm->index, est, a, sizeof(*p), bind);
if (ret)
return ret;