general protection fault in mptcp_sendmsg_frag

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    773dc50d Merge branch 'Xilinx-axienet-updates'
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1744ba4cd00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=dbc1ca9e55dc1f9f
dashboard link: https://syzkaller.appspot.com/bug?extid=409b0354a6ba83a86aaf
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16548404d00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=150c2914d00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+409b0354a6ba83a86aaf@xxxxxxxxxxxxxxxxxxxxxxxxx

general protection fault, probably for non-canonical address 0xdffffc0000000007: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f]
CPU: 0 PID: 8763 Comm: syz-executor836 Not tainted 5.11.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:mptcp_sendmsg_frag+0xa3f/0x1220 net/mptcp/protocol.c:1330
Code: 80 3c 02 00 0f 85 04 07 00 00 48 8b 04 24 48 8b 98 20 07 00 00 48 b8 00 00 00 00 00 fc ff df 48 8d 7b 38 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e d6 04 00 00 48 8d 7d 10 44 8b
RSP: 0018:ffffc90001dff7e8 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000007 RSI: 0000000000000000 RDI: 0000000000000038
RBP: ffff8880120d9e10 R08: 0000000000000001 R09: ffff8880120d9e10
R10: ffffed100241b3c4 R11: 0000000000000000 R12: ffff88801bf51800
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000008000
FS:  00007f0f56768700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000084 CR3: 000000001b547000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 mptcp_push_pending+0x2cc/0x650 net/mptcp/protocol.c:1477
 mptcp_sendmsg+0x1ffb/0x2830 net/mptcp/protocol.c:1692
 inet6_sendmsg+0x99/0xe0 net/ipv6/af_inet6.c:638
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:672
 sock_write_iter+0x289/0x3c0 net/socket.c:999
 call_write_iter include/linux/fs.h:1901 [inline]
 new_sync_write+0x426/0x650 fs/read_write.c:518
 vfs_write+0x791/0xa30 fs/read_write.c:605
 ksys_write+0x1ee/0x250 fs/read_write.c:658
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x4492d9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 a1 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:00007f0f56768318 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00000000004cf4c8 RCX: 00000000004492d9
RDX: 0000000000000001 RSI: 0000000020000000 RDI: 0000000000000003
RBP: 00000000004cf4c0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004cf4cc
R13: 00007fff4b6baf0f R14: 00007f0f56768400 R15: 0000000000022000
Modules linked in:
---[ end trace a30ad1b3e9650ce6 ]---
RIP: 0010:mptcp_sendmsg_frag+0xa3f/0x1220 net/mptcp/protocol.c:1330
Code: 80 3c 02 00 0f 85 04 07 00 00 48 8b 04 24 48 8b 98 20 07 00 00 48 b8 00 00 00 00 00 fc ff df 48 8d 7b 38 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e d6 04 00 00 48 8d 7d 10 44 8b
RSP: 0018:ffffc90001dff7e8 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000007 RSI: 0000000000000000 RDI: 0000000000000038
RBP: ffff8880120d9e10 R08: 0000000000000001 R09: ffff8880120d9e10
R10: ffffed100241b3c4 R11: 0000000000000000 R12: ffff88801bf51800
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000008000
FS:  00007f0f56768700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f97dbf78000 CR3: 000000001b547000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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