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From: Jane Chu <jane.chu@oracle.com>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: "pmladek@suse.com" <pmladek@suse.com>,
	"rostedt@goodmis.org" <rostedt@goodmis.org>,
	"senozhatsky@chromium.org" <senozhatsky@chromium.org>,
	"linux@rasmusvillemoes.dk" <linux@rasmusvillemoes.dk>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] vsprintf: protect kernel from panic due to non-canonical pointer dereference
Date: Mon, 17 Oct 2022 19:31:53 +0000	[thread overview]
Message-ID: <5d987403-a7bf-8996-d639-c99edeaabcdf@oracle.com> (raw)
In-Reply-To: <Y02sENwhtpsx5yhP@smile.fi.intel.com>

On 10/17/2022 12:25 PM, Andy Shevchenko wrote:
> On Mon, Oct 17, 2022 at 01:16:11PM -0600, Jane Chu wrote:
>> While debugging a separate issue, it was found that an invalid string
>> pointer could very well contain a non-canical address, such as
>> 0x7665645f63616465. In that case, this line of defense isn't enough
>> to protect the kernel from crashing due to general protection fault
>>
>> 	if ((unsigned long)ptr < PAGE_SIZE || IS_ERR_VALUE(ptr))
>>                  return "(efault)";
>>
>> So instead, use kern_addr_valid() to validate the string pointer.
> 
> How did you check that value of the (invalid string) pointer?
> 

In the bug scenario, the invalid string pointer was an out-of-bound 
string pointer. While the OOB referencing is fixed, the lingering issue 
is that the kernel ought to be able to protect itself, as the pointer 
contains a non-canonical address.  That said, I realized that not all 
architecture implement meaningful kern_addr_valid(), so this line
    if ((unsigned long)ptr < PAGE_SIZE || IS_ERR_VALUE(ptr))
is still need.  I'll send v2.

thanks,
-jane

> 


  reply	other threads:[~2022-10-17 19:32 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-10-17 19:16 [PATCH] vsprintf: protect kernel from panic due to non-canonical pointer dereference Jane Chu
2022-10-17 19:25 ` Andy Shevchenko
2022-10-17 19:31   ` Jane Chu [this message]
2022-10-18 12:45     ` Petr Mladek
2022-10-18 18:56       ` Jane Chu
2022-10-18 19:28         ` Randy Dunlap
2022-10-18 19:58           ` Jane Chu
2022-10-18 20:07         ` Andy Shevchenko
2022-10-18 20:30           ` Jane Chu
2022-10-18 20:49             ` Andy Shevchenko
2022-10-19 10:43               ` Haakon Bugge
2022-10-19 11:25                 ` Andy Shevchenko
2022-10-19 18:36               ` Jane Chu
2022-10-19 19:26                 ` Andy Shevchenko
2022-10-19 20:16                   ` Jane Chu
2022-10-20  7:44               ` Petr Mladek
2022-10-20  9:18                 ` Petr Mladek
2022-10-20 13:57                 ` Andy Shevchenko

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