From: joe@perches•com (Joe Perches)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] dmaengine: coh901318: fix integer overflow when shifting more than 32 places
Date: Tue, 04 Oct 2016 09:01:33 -0700 [thread overview]
Message-ID: <1475596893.2340.3.camel@perches.com> (raw)
In-Reply-To: <20161004153645.GG2467@localhost>
On Tue, 2016-10-04 at 21:06 +0530, Vinod Koul wrote:
> On Tue, Oct 04, 2016 at 02:23:51PM +0200, Linus Walleij wrote:
> > On Thu, Sep 29, 2016 at 8:06 PM, Joe Perches <joe@perches•com> wrote:
> > > On Thu, 2016-09-29 at 18:57 +0100, Colin King wrote:
> > > > Currently U300_DMA_CHANNELS is set to 40, meaning that the shift of 1 can
> > > > be more than 32 places, which leads to a 32 bit integer overflow. Fix this
> > > > by casting 1 to a u64 (the same type as started_channels) before shifting
> > > > it.
> > > trivia:
> > > > diff --git a/drivers/dma/coh901318.c b/drivers/dma/coh901318.c
> > > []
> > > > @@ -1353,7 +1353,7 @@ static ssize_t coh901318_debugfs_read(struct file *file, char __user *buf,
> > > > ? tmp += sprintf(tmp, "DMA -- enabled dma channels\n");
> > > >
> > > > ? for (i = 0; i < U300_DMA_CHANNELS; i++)
> > > > - if (started_channels & (1 << i))
> > > > + if (started_channels & ((u64)1 << i))
> > > Using
> > > ? if (started_channels & (1ULL << i))
> > > would be more common.
> > Even better (IMO):
> > #include <linux/bitops.h>
> > if (started_channels & BIT(i))
> > Apparently code is there to avoid the bit 31 problem, mea culpa.
> I have already applied this one, so feel free to send this as an update :)
BIT_ULL as it still needs to be u64 not unsigned long.
But if a change is really desired, please use it
consistently in the entire file and not just this
instance.
prev parent reply other threads:[~2016-10-04 16:01 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-29 17:57 [PATCH] dmaengine: coh901318: fix integer overflow when shifting more than 32 places Colin King
2016-09-29 18:06 ` Joe Perches
2016-10-04 12:23 ` Linus Walleij
2016-10-04 15:36 ` Vinod Koul
2016-10-04 16:01 ` Joe Perches [this message]
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