UBSAN: shift-out-of-bounds in xprt_calc_majortimeo

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    14240d4c Add linux-next specific files for 20201210
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1321cf17500000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6dbe20fdaa5aaebe
dashboard link: https://syzkaller.appspot.com/bug?extid=ba2e91df8f74809417fa
compiler:       gcc (GCC) 10.1.0-syz 20200507
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=174ecb9b500000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14ff9413500000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ba2e91df8f74809417fa@xxxxxxxxxxxxxxxxxxxxxxxxx

================================================================================
UBSAN: shift-out-of-bounds in net/sunrpc/xprt.c:658:14
shift exponent 536871232 is too large for 64-bit type 'long unsigned int'
CPU: 1 PID: 8494 Comm: syz-executor211 Not tainted 5.10.0-rc7-next-20201210-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x107/0x163 lib/dump_stack.c:120
 ubsan_epilogue+0xb/0x5a lib/ubsan.c:148
 __ubsan_handle_shift_out_of_bounds.cold+0xb1/0x181 lib/ubsan.c:395
 xprt_calc_majortimeo.isra.0.cold+0x17/0x46 net/sunrpc/xprt.c:658
 xprt_init_majortimeo net/sunrpc/xprt.c:686 [inline]
 xprt_request_init+0x486/0x9e0 net/sunrpc/xprt.c:1805
 xprt_do_reserve net/sunrpc/xprt.c:1815 [inline]
 xprt_reserve+0x18f/0x280 net/sunrpc/xprt.c:1836
 __rpc_execute+0x21d/0x1360 net/sunrpc/sched.c:891
 rpc_execute+0x230/0x350 net/sunrpc/sched.c:967
 rpc_run_task+0x5d0/0x8f0 net/sunrpc/clnt.c:1140
 rpc_call_sync+0xc6/0x1a0 net/sunrpc/clnt.c:1169
 rpc_ping net/sunrpc/clnt.c:2682 [inline]
 rpc_create_xprt+0x3f1/0x4a0 net/sunrpc/clnt.c:477
 rpc_create+0x354/0x670 net/sunrpc/clnt.c:593
 nfs_create_rpc_client+0x4eb/0x680 fs/nfs/client.c:536
 nfs_init_client fs/nfs/client.c:653 [inline]
 nfs_init_client+0x6d/0x100 fs/nfs/client.c:640
 nfs_get_client+0xcd7/0x1020 fs/nfs/client.c:430
 nfs_init_server.isra.0+0x2c0/0xed0 fs/nfs/client.c:692
 nfs_create_server+0x18f/0x650 fs/nfs/client.c:996
 nfs_try_get_tree+0x181/0x9f0 fs/nfs/super.c:939
 nfs_get_tree+0xaa1/0x1520 fs/nfs/fs_context.c:1350
 vfs_get_tree+0x89/0x2f0 fs/super.c:1496
 do_new_mount fs/namespace.c:2896 [inline]
 path_mount+0x12ae/0x1e70 fs/namespace.c:3227
 do_mount fs/namespace.c:3240 [inline]
 __do_sys_mount fs/namespace.c:3448 [inline]
 __se_sys_mount fs/namespace.c:3425 [inline]
 __x64_sys_mount+0x27f/0x300 fs/namespace.c:3425
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x440419
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 0f 83 7b 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffe282dde28 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 0000000000440419
RDX: 0000000020fb5ffc RSI: 0000000020343ff8 RDI: 0000000020000100
RBP: 00000000006ca018 R08: 000000002000a000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401c20
R13: 0000000000401cb0 R14: 0000000000000000 R15: 0000000000000000
================================================================================


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