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From: Rasmus Villemoes <linux@rasmusvillemoes•dk>
To: Francois Romieu <romieu@fr•zoreil.com>
Cc: David Miller <davem@davemloft•net>,
	netdev@vger•kernel.org, linux-kernel@vger•kernel.org
Subject: Re: [PATCH] net: sxgbe: fix error paths in sxgbe_platform_probe()
Date: Sun, 27 Mar 2016 23:40:24 +0200	[thread overview]
Message-ID: <87r3ev8urb.fsf@rasmusvillemoes.dk> (raw)
In-Reply-To: <20160327082254.GA10620@electric-eye.fr.zoreil.com> (Francois Romieu's message of "Sun, 27 Mar 2016 10:22:54 +0200")

On Sun, Mar 27 2016, Francois Romieu <romieu@fr•zoreil.com> wrote:

> Rasmus Villemoes <linux@rasmusvillemoes•dk> :
>> We need to use post-decrement to ensure that irq_dispose_mapping is
>> also called on priv->rxq[0]->irq_no; moreover, if one of the above for
>> loops failed already at i==0 (so we reach one of these labels with
>> that value of i), we'll enter an essentially infinite loop of
>> out-of-bounds accesses.
>> 
>> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes•dk>
>
> (ok, i is signed)
>
> Reviewed-by: Francois Romieu <romieu@fr•zoreil.com>
>

Thanks for reviewing, but just FTR I want to point out that it doesn't
matter whether i is signed or not in

  while (i--)

However, when i is signed, there's another slightly less popular variant
which is equivalent:

  while (--i >= 0)

(a precondition for their equivalence is that i has a non-negative value
before reaching the while statement).

Neither are equivalent to the almost-always broken

  while (--i)

Rasmus

next prev parent reply	other threads:[~2016-03-27 21:40 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-02-09 20:11 [PATCH 0/5] pre-decrement in error paths considered harmful Rasmus Villemoes
2016-02-09 20:11 ` [PATCH 3/5] net/mlx4: fix some error handling in mlx4_multi_func_init() Rasmus Villemoes
2016-02-10  9:40   ` Yishai Hadas
2016-02-10 18:15     ` Rasmus Villemoes
2016-02-11  9:29       ` Jack Morgenstein
2016-02-11 10:20         ` Jack Morgenstein
2016-02-11 16:02   ` Doug Ledford
2016-02-09 20:11 ` [PATCH 4/5] net: sxgbe: fix error paths in sxgbe_platform_probe() Rasmus Villemoes
2016-03-08 20:44   ` Rasmus Villemoes
2016-03-22 19:47     ` Rasmus Villemoes
2016-03-26 21:24       ` [PATCH] " Rasmus Villemoes
2016-03-27  8:22         ` Francois Romieu
2016-03-27 21:40           ` Rasmus Villemoes [this message]
2016-03-28  2:39           ` David Miller
2016-03-28  2:40         ` David Miller

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