From: Joe Perches <joe@perches.com>
To: "Gustavo A. R. Silva" <gustavo@embeddedor.com>,
William Breathitt Gray <vilhelm.gray@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Stephen Rothwell <sfr@canb.auug.org.au>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] linux/bitmap.h: fix potential sign-extension overflow
Date: Tue, 15 Oct 2019 12:44:52 -0700 [thread overview]
Message-ID: <5695bc78caf94d21b760960d4c1a34411cb4cb81.camel@perches.com> (raw)
In-Reply-To: <20191015184657.GA26541@embeddedor>
On Tue, 2019-10-15 at 13:46 -0500, Gustavo A. R. Silva wrote:
> In expression 0xff << offset, left shifting by more than 31 bits has
> undefined behavior. Notice that the shift amount, *offset*, can be as
> much as 63.
>
> Fix this by adding suffix ULL to integer 0xFF.
[]
> diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
[]
> @@ -520,7 +520,7 @@ static inline void bitmap_set_value8(unsigned long *map, unsigned long value,
> const size_t index = BIT_WORD(start);
> const unsigned long offset = start % BITS_PER_LONG;
>
> - map[index] &= ~(0xFF << offset);
> + map[index] &= ~(0xFFULL << offset);
BITS_PER_LONG is 32 and 0xFFULL is 64 bit
when compiled for 32 bit arches.
This should just be 0xFFUL and not ULL.
prev parent reply other threads:[~2019-10-15 19:44 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-15 18:46 [PATCH] linux/bitmap.h: fix potential sign-extension overflow Gustavo A. R. Silva
2019-10-15 19:44 ` Joe Perches [this message]
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