From: Thomas Gleixner <tglx@linutronix.de>
To: Jiri Slaby <jslaby@suse.cz>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] futex: make FUTEX_OP_OPARG_SHIFT unsigned
Date: Wed, 26 Oct 2016 13:22:29 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.20.1610261321510.4983@nanos> (raw)
In-Reply-To: <20161024102127.28220-1-jslaby@suse.cz>
On Mon, 24 Oct 2016, Jiri Slaby wrote:
> FUTEX_OP_OPARG_SHIFT is shifted left by 28 in futex_atomic_op_inuser and
> other places. Since FUTEX_OP_OPARG_SHIFT is 8, we actually do (8 << 28).
> But given both are ints, we perform operation with undefined behaviour
> about which UBSAN reports:
> UBSAN: Undefined behaviour in arch/x86/include/asm/futex.h:53:13
> shift exponent 776 is too large for 32-bit type 'int'
shift exponent 776 ????
Thanks,
tglx
prev parent reply other threads:[~2016-10-26 11:25 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-24 10:21 Jiri Slaby
2016-10-26 11:22 ` Thomas Gleixner [this message]
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