ACK: [PATCH 1/1] net: nfc: Fix NULL dereference on nfc_llcp_build_tlv fails

[Kleber Souza]

On 10.07.19 08:13, Tyler Hicks wrote:
> From: YueHaibing <yuehaibing at huawei.com>
> 
> KASAN report this:
> 
> BUG: KASAN: null-ptr-deref in nfc_llcp_build_gb+0x37f/0x540 [nfc]
> Read of size 3 at addr 0000000000000000 by task syz-executor.0/5401
> 
> CPU: 0 PID: 5401 Comm: syz-executor.0 Not tainted 5.0.0-rc7+ #45
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0xfa/0x1ce lib/dump_stack.c:113
>  kasan_report+0x171/0x18d mm/kasan/report.c:321
>  memcpy+0x1f/0x50 mm/kasan/common.c:130
>  nfc_llcp_build_gb+0x37f/0x540 [nfc]
>  nfc_llcp_register_device+0x6eb/0xb50 [nfc]
>  nfc_register_device+0x50/0x1d0 [nfc]
>  nfcsim_device_new+0x394/0x67d [nfcsim]
>  ? 0xffffffffc1080000
>  nfcsim_init+0x6b/0x1000 [nfcsim]
>  do_one_initcall+0xfa/0x5ca init/main.c:887
>  do_init_module+0x204/0x5f6 kernel/module.c:3460
>  load_module+0x66b2/0x8570 kernel/module.c:3808
>  __do_sys_finit_module+0x238/0x2a0 kernel/module.c:3902
>  do_syscall_64+0x147/0x600 arch/x86/entry/common.c:290
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x462e99
> Code: f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007f9cb79dcc58 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
> RAX: ffffffffffffffda RBX: 000000000073bf00 RCX: 0000000000462e99
> RDX: 0000000000000000 RSI: 0000000020000280 RDI: 0000000000000003
> RBP: 00007f9cb79dcc70 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007f9cb79dd6bc
> R13: 00000000004bcefb R14: 00000000006f7030 R15: 0000000000000004
> 
> nfc_llcp_build_tlv will return NULL on fails, caller should check it,
> otherwise will trigger a NULL dereference.
> 
> Reported-by: Hulk Robot <hulkci at huawei.com>
> Fixes: eda21f16a5ed ("NFC: Set MIU and RW values from CONNECT and CC LLCP frames")
> Fixes: d646960f7986 ("NFC: Initial LLCP support")
> Signed-off-by: YueHaibing <yuehaibing at huawei.com>
> Signed-off-by: David S. Miller <davem at davemloft.net>
> 
> CVE-2019-12818
> 
> (cherry picked from commit 58bdd544e2933a21a51eecf17c3f5f94038261b5)
> Signed-off-by: Tyler Hicks <tyhicks at canonical.com>

Acked-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>

> ---
>  net/nfc/llcp_commands.c | 20 ++++++++++++++++++++
>  net/nfc/llcp_core.c     | 24 ++++++++++++++++++++----
>  2 files changed, 40 insertions(+), 4 deletions(-)
> 
> diff --git a/net/nfc/llcp_commands.c b/net/nfc/llcp_commands.c
> index 6a196e438b6c..d1fc019e932e 100644
> --- a/net/nfc/llcp_commands.c
> +++ b/net/nfc/llcp_commands.c
> @@ -419,6 +419,10 @@ int nfc_llcp_send_connect(struct nfc_llcp_sock *sock)
>  						      sock->service_name,
>  						      sock->service_name_len,
>  						      &service_name_tlv_length);
> +		if (!service_name_tlv) {
> +			err = -ENOMEM;
> +			goto error_tlv;
> +		}
>  		size += service_name_tlv_length;
>  	}
>  
> @@ -429,9 +433,17 @@ int nfc_llcp_send_connect(struct nfc_llcp_sock *sock)
>  
>  	miux_tlv = nfc_llcp_build_tlv(LLCP_TLV_MIUX, (u8 *)&miux, 0,
>  				      &miux_tlv_length);
> +	if (!miux_tlv) {
> +		err = -ENOMEM;
> +		goto error_tlv;
> +	}
>  	size += miux_tlv_length;
>  
>  	rw_tlv = nfc_llcp_build_tlv(LLCP_TLV_RW, &rw, 0, &rw_tlv_length);
> +	if (!rw_tlv) {
> +		err = -ENOMEM;
> +		goto error_tlv;
> +	}
>  	size += rw_tlv_length;
>  
>  	pr_debug("SKB size %d SN length %zu\n", size, sock->service_name_len);
> @@ -484,9 +496,17 @@ int nfc_llcp_send_cc(struct nfc_llcp_sock *sock)
>  
>  	miux_tlv = nfc_llcp_build_tlv(LLCP_TLV_MIUX, (u8 *)&miux, 0,
>  				      &miux_tlv_length);
> +	if (!miux_tlv) {
> +		err = -ENOMEM;
> +		goto error_tlv;
> +	}
>  	size += miux_tlv_length;
>  
>  	rw_tlv = nfc_llcp_build_tlv(LLCP_TLV_RW, &rw, 0, &rw_tlv_length);
> +	if (!rw_tlv) {
> +		err = -ENOMEM;
> +		goto error_tlv;
> +	}
>  	size += rw_tlv_length;
>  
>  	skb = llcp_allocate_pdu(sock, LLCP_PDU_CC, size);
> diff --git a/net/nfc/llcp_core.c b/net/nfc/llcp_core.c
> index ef4026a23e80..4fa015208aab 100644
> --- a/net/nfc/llcp_core.c
> +++ b/net/nfc/llcp_core.c
> @@ -532,10 +532,10 @@ static u8 nfc_llcp_reserve_sdp_ssap(struct nfc_llcp_local *local)
>  
>  static int nfc_llcp_build_gb(struct nfc_llcp_local *local)
>  {
> -	u8 *gb_cur, *version_tlv, version, version_length;
> -	u8 *lto_tlv, lto_length;
> -	u8 *wks_tlv, wks_length;
> -	u8 *miux_tlv, miux_length;
> +	u8 *gb_cur, version, version_length;
> +	u8 lto_length, wks_length, miux_length;
> +	u8 *version_tlv = NULL, *lto_tlv = NULL,
> +	   *wks_tlv = NULL, *miux_tlv = NULL;
>  	__be16 wks = cpu_to_be16(local->local_wks);
>  	u8 gb_len = 0;
>  	int ret = 0;
> @@ -543,17 +543,33 @@ static int nfc_llcp_build_gb(struct nfc_llcp_local *local)
>  	version = LLCP_VERSION_11;
>  	version_tlv = nfc_llcp_build_tlv(LLCP_TLV_VERSION, &version,
>  					 1, &version_length);
> +	if (!version_tlv) {
> +		ret = -ENOMEM;
> +		goto out;
> +	}
>  	gb_len += version_length;
>  
>  	lto_tlv = nfc_llcp_build_tlv(LLCP_TLV_LTO, &local->lto, 1, &lto_length);
> +	if (!lto_tlv) {
> +		ret = -ENOMEM;
> +		goto out;
> +	}
>  	gb_len += lto_length;
>  
>  	pr_debug("Local wks 0x%lx\n", local->local_wks);
>  	wks_tlv = nfc_llcp_build_tlv(LLCP_TLV_WKS, (u8 *)&wks, 2, &wks_length);
> +	if (!wks_tlv) {
> +		ret = -ENOMEM;
> +		goto out;
> +	}
>  	gb_len += wks_length;
>  
>  	miux_tlv = nfc_llcp_build_tlv(LLCP_TLV_MIUX, (u8 *)&local->miux, 0,
>  				      &miux_length);
> +	if (!miux_tlv) {
> +		ret = -ENOMEM;
> +		goto out;
> +	}
>  	gb_len += miux_length;
>  
>  	gb_len += ARRAY_SIZE(llcp_magic);
>