netdev - Re: [PATCH ipsec] xfrm: add the missing verify_sec_ctx_len check in xfrm_add

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Date:   Thu, 13 Feb 2020 10:56:10 +0100
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     Xin Long <lucien.xin@...il.com>
CC:     <netdev@...r.kernel.org>, Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Trent Jaeger <tjaeger@....psu.edu>,
        Jamal Hadi Salim <hadi@...erus.ca>,
        Sabrina Dubroca <sd@...asysnail.net>,
        Hangbin Liu <liuhangbin@...il.com>
Subject: Re: [PATCH ipsec] xfrm: add the missing verify_sec_ctx_len check in
 xfrm_add_acquire

On Sun, Feb 09, 2020 at 09:16:38PM +0800, Xin Long wrote:
> Without doing verify_sec_ctx_len() check in xfrm_add_acquire(), it may be
> out-of-bounds to access uctx->ctx_str with uctx->ctx_len, as noticed by
> syz:
> 
>   BUG: KASAN: slab-out-of-bounds in selinux_xfrm_alloc_user+0x237/0x430
>   Read of size 768 at addr ffff8880123be9b4 by task syz-executor.1/11650
> 
>   Call Trace:
>    dump_stack+0xe8/0x16e
>    print_address_description.cold.3+0x9/0x23b
>    kasan_report.cold.4+0x64/0x95
>    memcpy+0x1f/0x50
>    selinux_xfrm_alloc_user+0x237/0x430
>    security_xfrm_policy_alloc+0x5c/0xb0
>    xfrm_policy_construct+0x2b1/0x650
>    xfrm_add_acquire+0x21d/0xa10
>    xfrm_user_rcv_msg+0x431/0x6f0
>    netlink_rcv_skb+0x15a/0x410
>    xfrm_netlink_rcv+0x6d/0x90
>    netlink_unicast+0x50e/0x6a0
>    netlink_sendmsg+0x8ae/0xd40
>    sock_sendmsg+0x133/0x170
>    ___sys_sendmsg+0x834/0x9a0
>    __sys_sendmsg+0x100/0x1e0
>    do_syscall_64+0xe5/0x660
>    entry_SYSCALL_64_after_hwframe+0x6a/0xdf
> 
> So fix it by adding the missing verify_sec_ctx_len check there.
> 
> Fixes: 980ebd25794f ("[IPSEC]: Sync series - acquire insert")
> Reported-by: Hangbin Liu <liuhangbin@...il.com>
> Signed-off-by: Xin Long <lucien.xin@...il.com>

Also applied, thanks a lot!