CVE-2019-12818 (C, published 2019-06-14T02:29Z)
Description: value: An issue was discovered in the Linux kernel before 4.20.15. The nfc_llcp_build_tlv function in net/nfc/llcp_commands.c may return NULL. If the caller does not check for this, it will trigger a NULL pointer dereference. This will cause denial of service. This affects nfc_llcp_build_gb in net/nfc/llcp_core.c.
Severity: MEDIUM (CVSS v3 base score: 7.5)
Weakness: CWE-476 \u2014 NULL Pointer Dereference
The product dereferences a pointer that it expects to be valid but is NULL.
Repository: https://github.com/torvalds/linux
Files changed:
net/nfc/llcp_commands.c
net/nfc/llcp_core.c
Commit message: net: nfc: Fix NULL dereference on nfc_llcp_build_tlv fails

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@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@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>


Vulnerable code:
	u8 *gb_cur, *version_tlv, version, version_length;
	u8 *lto_tlv, lto_length;
	u8 *wks_tlv, wks_length;
	u8 *miux_tlv, miux_length;

Fixed code:
		if (!service_name_tlv) {
			err = -ENOMEM;
			goto error_tlv;
		}
	if (!miux_tlv) {
		err = -ENOMEM;
		goto error_tlv;
	}
	if (!rw_tlv) {
		err = -ENOMEM;
		goto error_tlv;
	}
	if (!miux_tlv) {
		err = -ENOMEM;
		goto error_tlv;
	}
	if (!rw_tlv) {
		err = -ENOMEM;
		goto error_tlv;
	}
	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;
	if (!version_tlv) {
		ret = -ENOMEM;
		goto out;
	}
	if (!lto_tlv) {
		ret = -ENOMEM;
		goto out;
	}
	if (!wks_tlv) {
		ret = -ENOMEM;
		goto out;
	}
	if (!miux_tlv) {
		ret = -ENOMEM;
		goto out;
	}