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    SubjectRe: [syzbot] general protection fault in nfc_alloc_send_skb
    From
    On 16/01/2022 12:42, Hillf Danton wrote:
    > On Wed, 05 Jan 2022 06:25:31 -0800
    >> Hello,
    >>
    >> syzbot found the following issue on:
    >>
    >> HEAD commit: eec4df26e24e Merge tag 's390-5.16-6' of git://git.kernel.o..
    >> git tree: upstream
    >> console output: https://syzkaller.appspot.com/x/log.txt?x=149771a5b00000
    >> kernel config: https://syzkaller.appspot.com/x/.config?x=dc943eeb68074e3
    >> dashboard link: https://syzkaller.appspot.com/bug?extid=7f23bcddf626e0593a39
    >> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
    >> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=133e5e2bb00000
    >> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=152e6571b00000
    >>
    >> The issue was bisected to:
    >>
    >> commit c33b1cc62ac05c1dbb1cdafe2eb66da01c76ca8d
    >> Author: Xiaoming Ni <nixiaoming@huawei.com>
    >> Date: Thu Mar 25 03:51:10 2021 +0000
    >>
    >> nfc: fix refcount leak in llcp_sock_bind()
    >>
    >> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=16b92ba3b00000
    >> final oops: https://syzkaller.appspot.com/x/report.txt?x=15b92ba3b00000
    >> console output: https://syzkaller.appspot.com/x/log.txt?x=11b92ba3b00000
    >>
    >> IMPORTANT: if you fix the issue, please add the following tag to the commit:
    >> Reported-by: syzbot+7f23bcddf626e0593a39@syzkaller.appspotmail.com
    >> Fixes: c33b1cc62ac0 ("nfc: fix refcount leak in llcp_sock_bind()")
    >>
    >> general protection fault, probably for non-canonical address 0xdffffc00000000c2: 0000 [#1] PREEMPT SMP KASAN
    >> KASAN: null-ptr-deref in range [0x0000000000000610-0x0000000000000617]
    >> CPU: 1 PID: 7219 Comm: syz-executor408 Not tainted 5.16.0-rc7-syzkaller #0
    >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
    >> RIP: 0010:nfc_alloc_send_skb+0x3a/0x190 net/nfc/core.c:722
    >> Code: 54 41 89 d4 55 53 48 89 fb 48 8d ab 10 06 00 00 48 83 ec 08 e8 47 53 92 f8 48 89 ea 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e 14 01 00 00 48 8d bb 14 06 00
    >> RSP: 0018:ffffc9000ca97888 EFLAGS: 00010202
    >> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
    >> RDX: 00000000000000c2 RSI: ffffffff88e474b9 RDI: 0000000000000000
    >> RBP: 0000000000000610 R08: ffffc9000ca97938 R09: 0000000000000880
    >> R10: ffffffff88e6031d R11: 000000000000087f R12: 0000000000000000
    >> R13: 0000000000000082 R14: ffff88807ca8b000 R15: ffffc9000ca97938
    >> FS: 00007f6b81ae2700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
    >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    >> CR2: 00007fff1b2fd960 CR3: 000000007ca3a000 CR4: 00000000003506e0
    >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    >> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    >> Call Trace:
    >> <TASK>
    >> nfc_llcp_send_ui_frame+0x2c0/0x430 net/nfc/llcp_commands.c:759
    >> llcp_sock_sendmsg+0x2b9/0x3a0 net/nfc/llcp_sock.c:803
    >> sock_sendmsg_nosec net/socket.c:704 [inline]
    >> sock_sendmsg+0xcf/0x120 net/socket.c:724
    >> ____sys_sendmsg+0x331/0x810 net/socket.c:2409
    >> ___sys_sendmsg+0xf3/0x170 net/socket.c:2463
    >> __sys_sendmmsg+0x195/0x470 net/socket.c:2549
    >> __do_sys_sendmmsg net/socket.c:2578 [inline]
    >> __se_sys_sendmmsg net/socket.c:2575 [inline]
    >> __x64_sys_sendmmsg+0x99/0x100 net/socket.c:2575
    >> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
    >> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
    >> entry_SYSCALL_64_after_hwframe+0x44/0xae
    >> RIP: 0033:0x7f6b81b51f89
    >> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 15 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
    >> RSP: 002b:00007f6b81ae22f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
    >> RAX: ffffffffffffffda RBX: 0000000000000033 RCX: 00007f6b81b51f89
    >> RDX: 0000000000000006 RSI: 0000000020004540 RDI: 0000000000000003
    >> RBP: 00007f6b81bdb3f8 R08: 0000000000000000 R09: 0000000000000000
    >> R10: 0000000000000040 R11: 0000000000000246 R12: 00007f6b81bdb3f0
    >> R13: 93cb663f6753dadd R14: 4b973dfbaeacdab3 R15: f981dd66eb1318f7
    >> </TASK>
    >> Modules linked in:
    >> ---[ end trace 570920f865b173be ]---
    >> RIP: 0010:nfc_alloc_send_skb+0x3a/0x190 net/nfc/core.c:722
    >> Code: 54 41 89 d4 55 53 48 89 fb 48 8d ab 10 06 00 00 48 83 ec 08 e8 47 53 92 f8 48 89 ea 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e 14 01 00 00 48 8d bb 14 06 00
    >> RSP: 0018:ffffc9000ca97888 EFLAGS: 00010202
    >> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
    >> RDX: 00000000000000c2 RSI: ffffffff88e474b9 RDI: 0000000000000000
    >> RBP: 0000000000000610 R08: ffffc9000ca97938 R09: 0000000000000880
    >> R10: ffffffff88e6031d R11: 000000000000087f R12: 0000000000000000
    >> R13: 0000000000000082 R14: ffff88807ca8b000 R15: ffffc9000ca97938
    >> FS: 00007f6b81ae2700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
    >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    >> CR2: 00007fff1b2fd960 CR3: 000000007ca3a000 CR4: 00000000003506e0
    >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    >> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    >> ----------------
    >> Code disassembly (best guess):
    >> 0: 54 push %rsp
    >> 1: 41 89 d4 mov %edx,%r12d
    >> 4: 55 push %rbp
    >> 5: 53 push %rbx
    >> 6: 48 89 fb mov %rdi,%rbx
    >> 9: 48 8d ab 10 06 00 00 lea 0x610(%rbx),%rbp
    >> 10: 48 83 ec 08 sub $0x8,%rsp
    >> 14: e8 47 53 92 f8 callq 0xf8925360
    >> 19: 48 89 ea mov %rbp,%rdx
    >> 1c: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
    >> 23: fc ff df
    >> 26: 48 c1 ea 03 shr $0x3,%rdx
    >> * 2a: 0f b6 04 02 movzbl (%rdx,%rax,1),%eax <-- trapping instruction
    >> 2e: 84 c0 test %al,%al
    >> 30: 74 08 je 0x3a
    >> 32: 3c 03 cmp $0x3,%al
    >> 34: 0f 8e 14 01 00 00 jle 0x14e
    >> 3a: 48 rex.W
    >> 3b: 8d .byte 0x8d
    >> 3c: bb .byte 0xbb
    >> 3d: 14 06 adc $0x6,%al
    >>
    >>
    >> ---
    >> This report is generated by a bot. It may contain errors.
    >> See https://goo.gl/tpsmEJ for more information about syzbot.
    >> syzbot engineers can be reached at syzkaller@googlegroups.com.
    >>
    >> syzbot will keep track of this issue. See:
    >> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
    >> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
    >> syzbot can test patches for this issue, for details see:
    >> https://goo.gl/tpsmEJ#testing-patches
    >
    > Before sending frame out, check llcp dev bond to llcp sock and bail out in
    > case of invalid device.
    >
    > #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
    >
    > --- a/net/nfc/llcp_sock.c
    > +++ b/net/nfc/llcp_sock.c
    > @@ -798,6 +798,10 @@ static int llcp_sock_sendmsg(struct sock
    > return -EINVAL;
    > }
    >
    > + if (llcp_sock->dev == NULL) {
    > + release_sock(sk);
    > + return -EBADFD;
    > + }
    > release_sock(sk);
    >

    The patch looks the same as mine, except the test for ->dev is slightly
    later. Why sending the same set? My patch was already tested:

    2022/01/15 11:54
    https://github.com/krzk/linux 0b15d8c51584646c5fcd3a58053f11ac3b5f2cda OK

    2022/01/15 11:51
    https://github.com/krzk/linux 2e3adbe9c476cdfdc8da33ab83cf7a25715579f1 OK

    2022/01/15 11:46
    https://github.com/krzk/linux 6dcaa73089529a86e92d901c5f740b6529531c33 OK

    The test for llcp_sock->dev is equal to my test of local, because they
    are the same (assigned to NULL or to meaningful value), when accessed
    under lock.

    Best regards,
    Krzysztof

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