[PATCH v2] xfrm: policy: Fix possible user after free in __xfrm_policy_unlink
From: Yue Haibing
Date: Thu Feb 28 2019 - 01:39:12 EST
From: YueHaibing <yuehaibing@xxxxxxxxxx>
UBSAN report this:
UBSAN: Undefined behaviour in net/xfrm/xfrm_policy.c:1289:24
index 6 is out of range for type 'unsigned int [6]'
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.4.162-514.55.6.9.x86_64+ #13
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
0000000000000000 1466cf39b41b23c9 ffff8801f6b07a58 ffffffff81cb35f4
0000000041b58ab3 ffffffff83230f9c ffffffff81cb34e0 ffff8801f6b07a80
ffff8801f6b07a20 1466cf39b41b23c9 ffffffff851706e0 ffff8801f6b07ae8
Call Trace:
<IRQ> [<ffffffff81cb35f4>] __dump_stack lib/dump_stack.c:15 [inline]
<IRQ> [<ffffffff81cb35f4>] dump_stack+0x114/0x1a0 lib/dump_stack.c:51
[<ffffffff81d94225>] ubsan_epilogue+0x12/0x8f lib/ubsan.c:164
[<ffffffff81d954db>] __ubsan_handle_out_of_bounds+0x16e/0x1b2 lib/ubsan.c:382
[<ffffffff82a25acd>] __xfrm_policy_unlink+0x3dd/0x5b0 net/xfrm/xfrm_policy.c:1289
[<ffffffff82a2e572>] xfrm_policy_delete+0x52/0xb0 net/xfrm/xfrm_policy.c:1309
[<ffffffff82a3319b>] xfrm_policy_timer+0x30b/0x590 net/xfrm/xfrm_policy.c:243
[<ffffffff813d3927>] call_timer_fn+0x237/0x990 kernel/time/timer.c:1144
[<ffffffff813d8e7e>] __run_timers kernel/time/timer.c:1218 [inline]
[<ffffffff813d8e7e>] run_timer_softirq+0x6ce/0xb80 kernel/time/timer.c:1401
[<ffffffff8120d6f9>] __do_softirq+0x299/0xe10 kernel/softirq.c:273
[<ffffffff8120e676>] invoke_softirq kernel/softirq.c:350 [inline]
[<ffffffff8120e676>] irq_exit+0x216/0x2c0 kernel/softirq.c:391
[<ffffffff82c5edab>] exiting_irq arch/x86/include/asm/apic.h:652 [inline]
[<ffffffff82c5edab>] smp_apic_timer_interrupt+0x8b/0xc0 arch/x86/kernel/apic/apic.c:926
[<ffffffff82c5c985>] apic_timer_interrupt+0xa5/0xb0 arch/x86/entry/entry_64.S:735
<EOI> [<ffffffff81188096>] ? native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:52
[<ffffffff810834d7>] arch_safe_halt arch/x86/include/asm/paravirt.h:111 [inline]
[<ffffffff810834d7>] default_idle+0x27/0x430 arch/x86/kernel/process.c:446
[<ffffffff81085f05>] arch_cpu_idle+0x15/0x20 arch/x86/kernel/process.c:437
[<ffffffff8132abc3>] default_idle_call+0x53/0x90 kernel/sched/idle.c:92
[<ffffffff8132b32d>] cpuidle_idle_call kernel/sched/idle.c:156 [inline]
[<ffffffff8132b32d>] cpu_idle_loop kernel/sched/idle.c:251 [inline]
[<ffffffff8132b32d>] cpu_startup_entry+0x60d/0x9a0 kernel/sched/idle.c:299
[<ffffffff8113e119>] start_secondary+0x3c9/0x560 arch/x86/kernel/smpboot.c:245
The issue is triggered as this:
xfrm_add_policy
-->verify_newpolicy_info //check the index provided by user with XFRM_POLICY_MAX
//In my case, the index is 0x6E6BB6, so it pass the check.
-->xfrm_policy_construct //copy the user's policy and set xfrm_policy_timer
-->xfrm_policy_insert
--> __xfrm_policy_link //use the orgin dir, in my case is 2
--> xfrm_gen_index //generate policy index, there is 0x6E6BB6
then xfrm_policy_timer be fired
xfrm_policy_timer
--> xfrm_policy_id2dir //get dir from (policy index & 7), in my case is 6
--> xfrm_policy_delete
--> __xfrm_policy_unlink //access policy_count[dir], trigger out of range access
Add xfrm_policy_id2dir check in verify_newpolicy_info, make sure the computed dir is
valid, to fix the issue.
Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
Fixes: e682adf021be ("xfrm: Try to honor policy index if it's supplied by user")
Signed-off-by: YueHaibing <yuehaibing@xxxxxxxxxx>
---
v2: Fix index check in verify_newpolicy_info
---
net/xfrm/xfrm_user.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index a131f9f..aaa45c9 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -1424,7 +1424,8 @@ static int verify_newpolicy_info(struct xfrm_userpolicy_info *p)
ret = verify_policy_dir(p->dir);
if (ret)
return ret;
- if (p->index && ((p->index & XFRM_POLICY_MAX) != p->dir))
+ if (p->index && (((p->index & XFRM_POLICY_MAX) != p->dir) ||
+ (xfrm_policy_id2dir(p->index) >= XFRM_POLICY_MAX)))
return -EINVAL;
return 0;
--
2.7.0