linux-kernel - Re: UBSAN: Undefined behaviour in kernel/signal.c:911:6

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Message-ID: <20160514142417.GA6791@redhat.com>
Date:	Sat, 14 May 2016 16:24:18 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Meelis Roos <mroos@...ux.ee>
Cc:	Linux Kernel list <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: UBSAN: Undefined behaviour in kernel/signal.c:911:6

On 05/12, Meelis Roos wrote:
>
> This is from a 32-bit x86 computer with 4.6-rc* and UBSAN enabled. I am 
> also seeing it on some other 32-bit x86 machines. This one is SMP 
> AthlonMP.
>
> [  211.406263] ================================================================================
> [  211.406327] UBSAN: Undefined behaviour in kernel/signal.c:911:6
> [  211.406365] shift exponent 32 is too large for 32-bit type 'long unsigned int'

Hmm, indeed... Oh, and this needs other cleanups.

Thanks! I'll send the fix.

> [  211.406407] CPU: 1 PID: 1769 Comm: aptitude Not tainted 4.6.0-rc6-00072-g33656a1 #22
> [  211.406445] Hardware name: Unknown Unknown/S2462 THUNDER K7, BIOS Guinness-8    04/07/2003
> [  211.406486]  00000000 c134beac 00000007 f441be04 00000001 c1381f8b f441bdf8 00000020
> [  211.406724]  c1382516 c1700128 f441be08 00000020 c17b5288 00000002 00003233 c1a3d9c0
> [  211.406959]  00010000 024280ca 00363335 00000100 f441bea8 c11bf41b 00000000 00000000
> [  211.407194] Call Trace:
> [  211.407240]  [<c134beac>] ? dump_stack+0x45/0x69
> [  211.407278]  [<c1381f8b>] ? ubsan_epilogue+0xb/0x40
> [  211.407313]  [<c1382516>] ? __ubsan_handle_shift_out_of_bounds+0xd6/0x120
> [  211.407355]  [<c11bf41b>] ? path_openat+0x1db/0x1930
> [  211.407396]  [<c107dba5>] ? __sigqueue_alloc+0x75/0x190
> [  211.407495]  [<c107f7dc>] ? complete_signal+0x29c/0x3a0
> [  211.407593]  [<c1080167>] ? __send_signal.constprop.27+0x167/0x3b0
> [  211.407690]  [<c1081353>] ? do_send_sig_info+0x33/0x80
> [  211.407786]  [<c108146e>] ? do_send_specific+0x5e/0x90
> [  211.407881]  [<c1081523>] ? do_tkill+0x83/0xc0
> [  211.407978]  [<c1083d99>] ? SyS_tgkill+0x19/0x30
> [  211.408073]  [<c1002066>] ? do_fast_syscall_32+0xb6/0x1d0
> [  211.408172]  [<c164de9b>] ? sysenter_past_esp+0x40/0x6a
> [  211.408266] ================================================================================
> 
> 
> -- 
> Meelis Roos (mroos@...ux.ee)