From: Al Viro <viro@zeniv.linux.org.uk>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Joel Stanley <joel@jms.id.au>, Andrew Jeffery <andrew@aj.id.au>,
"Chia-Wei, Wang" <chiawei_wang@aspeedtech.com>,
Jae Hyun Yoo <jae.hyun.yoo@intel.com>,
John Wang <wangzhiqiang.bj@bytedance.com>,
Brad Bishop <bradleyb@fuzziesquirrel.com>,
Patrick Venture <venture@google.com>,
Benjamin Fair <benjaminfair@google.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Robert Lippert <rlippert@google.com>,
linux-aspeed@lists.ozlabs.org, linux-kernel@vger.kernel.org,
kernel-janitors@vger.kernel.org
Subject: Re: [PATCH] soc: aspeed: fix a ternary sign expansion bug
Date: Thu, 22 Apr 2021 09:24:59 +0000 [thread overview]
Message-ID: <YIFA68mfUTSMczp0@zeniv-ca.linux.org.uk> (raw)
In-Reply-To: <YIE90PSXsMTa2Y8n@mwanda>
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.
WARNING: multiple messages have this Message-ID (diff)
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 09:24:59 +0000 [thread overview]
Message-ID: <YIFA68mfUTSMczp0@zeniv-ca.linux.org.uk> (raw)
In-Reply-To: <YIE90PSXsMTa2Y8n@mwanda>
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.
next prev parent reply other threads:[~2021-04-22 9:25 UTC|newest]
Thread overview: 30+ 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 9:11 ` Dan Carpenter
2021-04-22 9:24 ` Al Viro [this message]
2021-04-22 9:24 ` Al Viro
2021-04-22 9:26 ` Al Viro
2021-04-22 9:26 ` Al Viro
2021-04-22 14:56 ` Patrick Venture
2021-04-22 14:56 ` Patrick Venture
2021-04-22 16:21 ` David Laight
2021-04-22 16:21 ` David Laight
2021-04-23 0:07 ` Joel Stanley
2021-04-23 0:07 ` Joel Stanley
2021-04-23 7:43 ` Dan Carpenter
2021-04-23 7:43 ` Dan Carpenter
2021-04-23 10:45 ` Sergey Organov
2021-04-23 10:45 ` Sergey Organov
2021-04-23 10:54 ` David Laight
2021-04-23 10:54 ` David Laight
2021-04-23 11:03 ` AW: " Walter Harms
2021-04-23 11:03 ` Walter Harms
2021-04-23 14:40 ` Sergey Organov
2021-04-23 14:40 ` Sergey Organov
2021-04-23 14:55 ` David Laight
2021-04-23 14:55 ` David Laight
2021-04-23 15:24 ` Dan Carpenter
2021-04-23 15:24 ` Dan Carpenter
2021-04-23 11:14 ` Dan Carpenter
2021-04-23 11:14 ` Dan Carpenter
-- strict thread matches above, loose matches on Subject: below --
2021-04-23 0:09 Joel Stanley
2021-04-23 9:30 ` patchwork-bot+linux-soc
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