From: Jun Sun <jsun@mvista.com>
To: Ralf Baechle <ralf@oss.sgi.com>
Cc: linux-mips <linux-mips@oss.sgi.com>
Subject: Re: what is the right behavior of copy_to_user(0x0, ..., ...)?
Date: Fri, 03 May 2002 16:41:56 -0700 [thread overview]
Message-ID: <3CD32044.9040109@mvista.com> (raw)
In-Reply-To: 20020503162337.A27366@dea.linux-mips.net
Ralf Baechle wrote:
> On Fri, May 03, 2002 at 02:46:19PM -0700, Jun Sun wrote:
>
>
>>When running LTP, I notice that recent kernel has a kernel access fault:
>>
>><1>Unable to handle kernel paging request at virtual address 00000000, epc
>>== 80273860, ra == 80205aa4
>>
>
> Well, decode the oops message. The question is what is at 0x80273860?
>
0x80273860 is copy_bytes in arch/mips/lib/memcpy.S, which is reached through __copy_user.
The faulting instruction, not suprisingly, is writing a byte to the
destination at 0x0.
Anybody can try to call copy_to_user(0x0, ...) inside kernel and see the
scene. The question here is whether we should reach do_page_fault() and
terminate calling process or try to catch the fault and return some meaningful
error.
It appears earlier version of kernel does not have this problem. I have not
fully figured out why.
Jun
next prev parent reply other threads:[~2002-05-03 23:42 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-05-03 21:46 what is the right behavior of copy_to_user(0x0, ..., ...)? Jun Sun
2002-05-03 23:23 ` Ralf Baechle
2002-05-03 23:41 ` Jun Sun [this message]
2002-05-04 1:40 ` Ralf Baechle
2002-05-06 18:18 ` Jun Sun
2002-05-08 3:16 ` Ralf Baechle
2002-05-07 8:47 ` Carsten Langgaard
2002-05-06 17:53 ` Ralf Baechle
2002-05-06 19:44 ` Ralf Baechle
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