Re: [PATCH] net: mac802154: Fix null pointer dereference

[Alexander Aring]

Hi,

On Wed, 3 Mar 2021 at 11:28, Pavel Skripkin <paskripkin@xxxxxxxxx> wrote:
>
> syzbot found general protection fault in crypto_destroy_tfm()[1].
> It was caused by wrong clean up loop in llsec_key_alloc().
> If one of the tfm array members won't be initialized it will cause
> NULL dereference in crypto_destroy_tfm().
>
> Call Trace:
>  crypto_free_aead include/crypto/aead.h:191 [inline] [1]
>  llsec_key_alloc net/mac802154/llsec.c:156 [inline]
>  mac802154_llsec_key_add+0x9e0/0xcc0 net/mac802154/llsec.c:249
>  ieee802154_add_llsec_key+0x56/0x80 net/mac802154/cfg.c:338
>  rdev_add_llsec_key net/ieee802154/rdev-ops.h:260 [inline]
>  nl802154_add_llsec_key+0x3d3/0x560 net/ieee802154/nl802154.c:1584
>  genl_family_rcv_msg_doit+0x228/0x320 net/netlink/genetlink.c:739
>  genl_family_rcv_msg net/netlink/genetlink.c:783 [inline]
>  genl_rcv_msg+0x328/0x580 net/netlink/genetlink.c:800
>  netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2502
>  genl_rcv+0x24/0x40 net/netlink/genetlink.c:811
>  netlink_unicast_kernel net/netlink/af_netlink.c:1312 [inline]
>  netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1338
>  netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1927
>  sock_sendmsg_nosec net/socket.c:654 [inline]
>  sock_sendmsg+0xcf/0x120 net/socket.c:674
>  ____sys_sendmsg+0x6e8/0x810 net/socket.c:2350
>  ___sys_sendmsg+0xf3/0x170 net/socket.c:2404
>  __sys_sendmsg+0xe5/0x1b0 net/socket.c:2433
>  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> Signed-off-by: Pavel Skripkin <paskripkin@xxxxxxxxx>
> Reported-by: syzbot+12cf5fbfdeba210a89dd@xxxxxxxxxxxxxxxxxxxxxxxxx
> ---
>  net/mac802154/llsec.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/mac802154/llsec.c b/net/mac802154/llsec.c
> index 585d33144c33..6709f186f777 100644
> --- a/net/mac802154/llsec.c
> +++ b/net/mac802154/llsec.c
> @@ -151,7 +151,7 @@ llsec_key_alloc(const struct ieee802154_llsec_key *template)
>  err_tfm0:
>         crypto_free_sync_skcipher(key->tfm0);
>  err_tfm:
> -       for (i = 0; i < ARRAY_SIZE(key->tfm); i++)
> +       for (; i >= 0; i--)
>                 if (key->tfm[i])

I think this need to be:

if (!IS_ERR_OR_NULL(key->tfm[i]))

otherwise we still run into issues for the current iterator when
key->tfm[i] is in range of IS_ERR().

- Alex