netdev - Re: [PATCH net] lib: packing: fix shift wrapping in bit

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Date:   Wed, 7 Dec 2022 15:21:04 +0300
From:   Dan Carpenter <error27@...il.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH net] lib: packing: fix shift wrapping in bit_reverse()

On Wed, Dec 07, 2022 at 02:19:36PM +0200, Vladimir Oltean wrote:
> On Wed, Dec 07, 2022 at 02:23:28PM +0300, Dan Carpenter wrote:
> > The bit_reverse() function is clearly supposed to be able to handle
> > 64 bit values, but the types for "(1 << i)" and "bit << (width - i - 1)"
> > are not enough to handle more than 32 bits.
> > 
> > Fixes: 554aae35007e ("lib: Add support for generic packing operations")
> > Signed-off-by: Dan Carpenter <error27@...il.com>
> > ---
> >  lib/packing.c | 5 ++---
> >  1 file changed, 2 insertions(+), 3 deletions(-)
> > 
> > diff --git a/lib/packing.c b/lib/packing.c
> > index 9a72f4bbf0e2..9d7418052f5a 100644
> > --- a/lib/packing.c
> > +++ b/lib/packing.c
> > @@ -32,12 +32,11 @@ static int get_reverse_lsw32_offset(int offset, size_t len)
> >  static u64 bit_reverse(u64 val, unsigned int width)
> >  {
> >  	u64 new_val = 0;
> > -	unsigned int bit;
> >  	unsigned int i;
> >  
> >  	for (i = 0; i < width; i++) {
> > -		bit = (val & (1 << i)) != 0;
> > -		new_val |= (bit << (width - i - 1));
> > +		if (val & BIT_ULL(1))
> 
> hmm, why 1 and not i?

Because I'm a moron.  Let me resend.

regards,
dan carpenter