Hello, got this today at a stable Gentoo Linux with recent kernel :
Nov 1 05:29:46 mr-fox kernel: [231282.542520] ================================================================================ Nov 1 05:29:46 mr-fox kernel: [231282.542523] UBSAN: Undefined behaviour in ./arch/x86/include/asm/futex.h:53:13 Nov 1 05:29:46 mr-fox kernel: [231282.542525] shift exponent -849 is negative Nov 1 05:29:46 mr-fox kernel: [231282.542527] CPU: 3 PID: 15032 Comm: futex Not tainted 4.13.10 #13 Nov 1 05:29:46 mr-fox kernel: [231282.542528] Hardware name: /DX79TO, BIOS SIX7910J.86A.0650.2014.0307.0138 03/07/2014 Nov 1 05:29:46 mr-fox kernel: [231282.542529] Call Trace: Nov 1 05:29:46 mr-fox kernel: [231282.542535] dump_stack+0x60/0x9a Nov 1 05:29:46 mr-fox kernel: [231282.542539] ? val_is_negative+0x2b/0x50 Nov 1 05:29:46 mr-fox kernel: [231282.542540] ubsan_epilogue+0xd/0x40 Nov 1 05:29:46 mr-fox kernel: [231282.542542] __ubsan_handle_shift_out_of_bounds+0x10d/0x170 Nov 1 05:29:46 mr-fox kernel: [231282.542545] ? get_futex_key+0x38a/0x6e0 Nov 1 05:29:46 mr-fox kernel: [231282.542546] do_futex+0xd72/0x1380 Nov 1 05:29:46 mr-fox kernel: [231282.542547] ? do_futex+0xd72/0x1380 Nov 1 05:29:46 mr-fox kernel: [231282.542548] SyS_futex+0x7a/0x180 Nov 1 05:29:46 mr-fox kernel: [231282.542551] ? SyS_write+0x4f/0xc0 Nov 1 05:29:46 mr-fox kernel: [231282.542554] entry_SYSCALL_64_fastpath+0x13/0x94 Nov 1 05:29:46 mr-fox kernel: [231282.542555] RIP: 0033:0x7fed8a79c829 Nov 1 05:29:46 mr-fox kernel: [231282.542556] RSP: 002b:00007fffadf04968 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca Nov 1 05:29:46 mr-fox kernel: [231282.542557] RAX: ffffffffffffffda RBX: 00007fed8aa55ae0 RCX: 00007fed8a79c829 Nov 1 05:29:46 mr-fox kernel: [231282.542558] RDX: badda7a0facefeed RSI: 0000000000000005 RDI: 00007fed8ae2bffc Nov 1 05:29:46 mr-fox kernel: [231282.542559] RBP: 0000000000001011 R08: 00007fed8ae25ffc R09: 00000000a0caffee Nov 1 05:29:46 mr-fox kernel: [231282.542560] R10: 000000000000000b R11: 0000000000000246 R12: 0000000000000000 Nov 1 05:29:46 mr-fox kernel: [231282.542560] R13: 00007fed8aa55b38 R14: 0000000000000000 R15: 0000000000001030 Nov 1 05:29:46 mr-fox kernel: [231282.542561] ================================================================================ -- Toralf PGP C4EACDDE 0076E94E