Re: [PATCH] xfrm: correctly check policy index in verify_newpolicy_info

[YueHaibing <yuehaibing@huawei.com>]

Pls ignore this, sorry

On 2019/2/25 17:27, Yue Haibing wrote:
> From: YueHaibing <yuehaibing@huawei.com>
> 
> 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
> 
> xfrm_add_policy calls verify_newpolicy_info to check user's policy info,
> but it doest check policy index correcly, if the policy index(ex. 6) is great
> than XFRM_POLICY_MAX which is 3 for now, the validation check will be bypassed.
> It will trigger out of bounds access.
> 
> Reported-by: Hulk Robot <hulkci@huawei.com>
> Fixes: e682adf021be ("xfrm: Try to honor policy index if it's supplied by user")
> Signed-off-by: YueHaibing <yuehaibing@huawei.com>
> ---
>  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..c2de950 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->index & XFRM_POLICY_MAX) != p->dir))
>  		return -EINVAL;
>  
>  	return 0;
>