net/nfc: GPF in llcp_sock_getname

[Dmitry Vyukov]

Hello,

The following program triggers GPF in llcp_sock_getname:

// autogenerated by syzkaller (http://github.com/google/syzkaller)
#include <unistd.h>
#include <sys/syscall.h>
#include <string.h>
#include <stdint.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <linux/nfc.h>
#include <pthread.h>

int fd;

void *thr(void *arg)
{
        struct sockaddr_nfc_llcp sa;
        sa.sa_family = AF_NFC;
        sa.dev_idx = 0;
        sa.target_idx = 0x24a8;
        sa.nfc_protocol = 0;
        sa.dsap = 0;
        sa.ssap = 2;
        sa.service_name[0] = 7;
        sa.service_name[1] = 9;
        sa.service_name[2] = 3;
        sa.service_name_len = 3;
        bind(fd, (struct sockaddr*)&sa, sizeof(sa));
        return 0;
}

int main()
{
        fd = socket(AF_NFC, 0x2ul, 0x1ul);
        pthread_t th;
        pthread_create(&th, 0, thr, 0);
        struct sockaddr_nfc_llcp sa;
        int len = sizeof(sa);
        getsockname(fd, (struct sockaddr*)&sa, &len);
        return 0;
}


kasan: GPF could be caused by NULL-ptr deref or user memory
accessgeneral protection fault: 0000 [#51] SMP KASAN
Modules linked in:
CPU: 2 PID: 4207 Comm: a.out Not tainted 4.4.0-rc7+ #184
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
task: ffff8800683e9780 ti: ffff880064c70000 task.ti: ffff880064c70000
RIP: 0010:[<ffffffff816d1d5b>]  [<ffffffff816d1d5b>]
kasan_report_error+0x1b/0x560
RSP: 0018:ffff880064c77c90  EFLAGS: 00010286
RAX: dffffc0000000000 RBX: 0000000000000003 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 0000000000000003 RDI: ffff880064c77c98
RBP: ffff880064c77cc0 R08: ffffed000c98efd6 R09: ffff880064c77e58
R10: ffff8800639670a0 R11: ffff880063967098 R12: ffff880064c77e6a
R13: 0000000000000000 R14: 0000000000000000 R15: ffff880063967088
FS:  00000000018ca880(0063) GS:ffff88006da00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 000000c8200012e0 CR3: 0000000064c59000 CR4: 00000000000006e0
Stack:
 ffffffff816d25d4 0000000000000000 0000000000000018 0000000000000003
 0000000300004000 ffffffff816d17ed ffff880064c77cd0 ffffffff816d1264
 ffff880064c77cf8 ffffffff816d17ed 0000000000000000 ffff880064c77e58
Call Trace:
 [<     inline     >] check_memory_region mm/kasan/kasan.c:264
 [<ffffffff816d1264>] __asan_loadN+0x124/0x1a0 mm/kasan/kasan.c:512
 [<ffffffff816d17ed>] memcpy+0x1d/0x40 mm/kasan/kasan.c:297
 [<ffffffff85becf44>] llcp_sock_getname+0x424/0x600 net/nfc/llcp_sock.c:519
 [<ffffffff84b5ab4d>] SYSC_getsockname+0x1bd/0x220 net/socket.c:1570
 [<ffffffff84b60244>] SyS_getsockname+0x24/0x30 net/socket.c:1555
 [<ffffffff85c8eaf6>] entry_SYSCALL_64_fastpath+0x16/0x7a
arch/x86/entry/entry_64.S:185
Code: 48 01 c7 e8 38 2b fc ff 5d c3 66 0f 1f 44 00 00 48 8b 17 48 b9
00 00 00 00 00 fc ff df 48 8b 77 10 48 89 d0 48 c1 e8 03 48 01 c8 <80>
38 00 75 1d 48 01 d6 eb 13 48 83 c2 08 48 89 d0 48 c1 e8 03
RIP  [<ffffffff816d1d5b>] kasan_report_error+0x1b/0x560 mm/kasan/report.c:214
 RSP <ffff880064c77c90>
---[ end trace b0c68fb0d02b9447 ]---

On commit 8513342170278468bac126640a5d2d12ffbff106 (Dec 28).
GPF seems to be caused by a data race on socket state.
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