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From: Al Viro <viro@zeniv.linux.org.uk>
To: linux-aspeed@lists.ozlabs.org
Subject: [PATCH] soc: aspeed: fix a ternary sign expansion bug
Date: Thu, 22 Apr 2021 09:26:27 +0000	[thread overview]
Message-ID: <YIFBQ50rcZO3NDFD@zeniv-ca.linux.org.uk> (raw)
In-Reply-To: <YIFA68mfUTSMczp0@zeniv-ca.linux.org.uk>

On Thu, Apr 22, 2021 at 09:24:59AM +0000, Al Viro wrote:
> On Thu, Apr 22, 2021 at 12:11:44PM +0300, Dan Carpenter wrote:
> > The intent here was to return negative error codes but it actually
> > returns positive values.  The problem is that type promotion with
> > ternary operations is quite complicated.
> > 
> > "ret" is an int.  "copied" is a u32.  And the snoop_file_read() function
> > returns long.  What happens is that "ret" is cast to u32 and becomes
> > positive then it's cast to long and it's still positive.
> > 
> > Fix this by removing the ternary so that "ret" is type promoted directly
> > to long.
> 
> Hmm...  Let's grep for kfifo_to_user() - smells like a possible recurring bug...
> Yup -
> 
> samples/kfifo/bytestream-example.c:138: ret = kfifo_to_user(&test, buf, count, &copied);
> samples/kfifo/inttype-example.c:131:    ret = kfifo_to_user(&test, buf, count, &copied);
> samples/kfifo/record-example.c:145:     ret = kfifo_to_user(&test, buf, count, &copied);
> 
> All three are exactly like that one.

Nevermind, you've already caught and posted that bunch.  Sorry for noise...

  reply	other threads:[~2021-04-22  9:26 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-22  9:11 [PATCH] soc: aspeed: fix a ternary sign expansion bug Dan Carpenter
2021-04-22  9:24 ` Al Viro
2021-04-22  9:26   ` Al Viro [this message]
2021-04-22 14:56 ` Patrick Venture
2021-04-22 16:21 ` David Laight
2021-04-23  0:07   ` Joel Stanley
2021-04-23  7:43   ` Dan Carpenter
2021-04-23 10:45   ` Sergey Organov
2021-04-23 10:54     ` David Laight
2021-04-23 11:03       ` AW: " Walter Harms
2021-04-23 14:40         ` Sergey Organov
2021-04-23 14:55           ` David Laight
2021-04-23 15:24           ` Dan Carpenter
2021-04-23 11:14     ` Dan Carpenter

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