linux-kernel - Re: [PATCH 5/9] kprobes: Silence DEBUG_STRICT_USER_COPY

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Date:	Fri, 13 May 2011 09:29:34 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	linux-kernel@...r.kernel.org,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 5/9] kprobes: Silence DEBUG_STRICT_USER_COPY_CHECKS=y
 warning

(2011/05/13 8:50), Stephen Boyd wrote:
> Enabling DEBUG_STRICT_USER_COPY_CHECKS causes the following
> warning:
> 
> In file included from arch/x86/include/asm/uaccess.h:573,
>                  from kernel/kprobes.c:55:
> In function 'copy_from_user',
>     inlined from 'write_enabled_file_bool' at
>     kernel/kprobes.c:2191:
> arch/x86/include/asm/uaccess_64.h:65:
> warning: call to 'copy_from_user_overflow' declared with
> attribute warning: copy_from_user() buffer size is not provably
> correct
> 
> presumably due to buf_size being signed causing GCC to fail to
> see that buf_size can't become negative.

Good catch! At least, since the "count" is size_t, buf_size
should be size_t too.

Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>

Thank you!

> 
> Cc: Ananth N Mavinakayanahalli <ananth@...ibm.com>
> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
> Cc: David S. Miller <davem@...emloft.net>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
> ---
>  kernel/kprobes.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 7798181..1938187 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -2185,7 +2185,7 @@ static ssize_t write_enabled_file_bool(struct file *file,
>  	       const char __user *user_buf, size_t count, loff_t *ppos)
>  {
>  	char buf[32];
> -	int buf_size;
> +	size_t buf_size;
>  
>  	buf_size = min(count, (sizeof(buf)-1));
>  	if (copy_from_user(buf, user_buf, buf_size))


-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com
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