net: nfc: Fix NULL dereference on nfc_llcp_build_tlv fails [Linux 5.0]

net: nfc: Fix NULL dereference on nfc_llcp_build_tlv fails [Linux 5.0]

This Linux kernel change "net: nfc: Fix NULL dereference on nfc_llcp_build_tlv fails" is included in the Linux 5.0 release. This change is authored by YueHaibing <yuehaibing [at] huawei.com> on Fri Feb 22 15:37:58 2019 +0800. The commit for this change in Linux stable tree is 58bdd54 (patch).

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 <[email protected]>
Fixes: eda21f16a5ed ("NFC: Set MIU and RW values from CONNECT and CC LLCP frames")
Fixes: d646960f7986 ("NFC: Initial LLCP support")
Signed-off-by: YueHaibing <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

There are 44 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 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 6a196e4..d1fc019e 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 ef4026a..4fa0152 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);

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