linux-kernel - UBSAN warnings in kernel/sysctl.c:2215:10 for 4.10.13

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Date:   Mon, 1 May 2017 17:11:36 +0200
From:   Toralf Förster <toralf.foerster@....de>
To:     Linux Kernel <linux-kernel@...r.kernel.org>
Subject: UBSAN warnings in kernel/sysctl.c:2215:10 for 4.10.13

Whilst I'm wondering about missing kern.log entries of my server for about 13 hours within last night I stumbled over this :


May  1 05:53:19 mr-fox kernel: [63395.062218] ================================================================================
May  1 05:53:19 mr-fox kernel: [63395.062221] UBSAN: Undefined behaviour in kernel/sysctl.c:2215:10
May  1 05:53:19 mr-fox kernel: [63395.062223] load of value 255 is not a valid value for type '_Bool'
May  1 05:53:19 mr-fox kernel: [63395.062226] CPU: 3 PID: 12243 Comm: sysctl Not tainted 4.10.13 #4
May  1 05:53:19 mr-fox kernel: [63395.062227] Hardware name:                  /DX79TO, BIOS SIX7910J.86A.0650.2014.0307.0138 03/07/2014
May  1 05:53:19 mr-fox kernel: [63395.062228] Call Trace:
May  1 05:53:19 mr-fox kernel: [63395.062236]  dump_stack+0x60/0x9c
May  1 05:53:19 mr-fox kernel: [63395.062239]  ubsan_epilogue+0xd/0x40
May  1 05:53:19 mr-fox kernel: [63395.062242]  __ubsan_handle_load_invalid_value+0x75/0xa0
May  1 05:53:19 mr-fox kernel: [63395.062245]  ? terminate_walk+0x10a/0x1b0
May  1 05:53:19 mr-fox kernel: [63395.062249]  __do_proc_dointvec+0x447/0x4d0
May  1 05:53:19 mr-fox kernel: [63395.062250]  ? do_proc_dointvec_conv+0x1f0/0x1f0
May  1 05:53:19 mr-fox kernel: [63395.062252]  proc_douintvec+0x3f/0x70
May  1 05:53:19 mr-fox kernel: [63395.062254]  ? do_proc_dointvec_conv+0x1f0/0x1f0
May  1 05:53:19 mr-fox kernel: [63395.062256]  ? sysctl_perm+0x7e/0xe0
May  1 05:53:19 mr-fox kernel: [63395.062258]  proc_sys_call_handler+0xe4/0x130
May  1 05:53:19 mr-fox kernel: [63395.062259]  proc_sys_read+0xc/0x10
May  1 05:53:19 mr-fox kernel: [63395.062262]  __vfs_read+0x54/0x2a0
May  1 05:53:19 mr-fox kernel: [63395.062263]  vfs_read+0xbc/0x210
May  1 05:53:19 mr-fox kernel: [63395.062265]  SyS_read+0x50/0xc0
May  1 05:53:19 mr-fox kernel: [63395.062269]  entry_SYSCALL_64_fastpath+0x13/0x94
May  1 05:53:19 mr-fox kernel: [63395.062270] RIP: 0033:0x7f202f39da40
May  1 05:53:19 mr-fox kernel: [63395.062272] RSP: 002b:00007ffcf606b188 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
May  1 05:53:19 mr-fox kernel: [63395.062274] RAX: ffffffffffffffda RBX: 0000000000002010 RCX: 00007f202f39da40
May  1 05:53:19 mr-fox kernel: [63395.062275] RDX: 0000000000000400 RSI: 000000000070c020 RDI: 0000000000000006
May  1 05:53:19 mr-fox kernel: [63395.062276] RBP: 00007f202f66baa0 R08: 0000000000000411 R09: 0000000000000000
May  1 05:53:19 mr-fox kernel: [63395.062278] R10: 0000000000006d50 R11: 0000000000000246 R12: 00007f202f66bed1
May  1 05:53:19 mr-fox kernel: [63395.062278] R13: 00000000000000e1 R14: 0000000000000000 R15: 0000000000000000
May  1 05:53:19 mr-fox kernel: [63395.062279] ================================================================================



Line 2215 was last changed 7 years ago:

	err = proc_put_long(&buffer, &left, lval, neg);

so is UBSAN wrong here ?

-- 
Toralf
PGP C4EACDDE 0076E94E