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Re: [PATRCH] janitor: hermes: delete verify_area call

To: David Gibson <hermes@xxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [PATRCH] janitor: hermes: delete verify_area call
From: "Randy.Dunlap" <rddunlap@xxxxxxxx>
Date: Mon, 29 Sep 2003 13:06:08 -0700
Cc: netdev@xxxxxxxxxxx, jgarzik@xxxxxxxxx
In-reply-to: <20030929052925.GA5037@zax>
Organization: OSDL
References: <20030925215902.57f53822.rddunlap@xxxxxxxx> <20030929052925.GA5037@zax>
Sender: netdev-bounce@xxxxxxxxxxx
On Mon, 29 Sep 2003 15:29:25 +1000 David Gibson <hermes@xxxxxxxxxxxxxxxxxxxxx> 
wrote:

| On Thu, Sep 25, 2003 at 09:59:02PM -0700, Randy.Dunlap wrote:
| > 
| > Hi,
| > Please apply to 2.6.0-test5-current.
| > 
| > Thanks,
| 
| Sorry, can you clarify why this verify_area() is not needed?


Sure, I'll try to do that.
There are several related reasons for it.

Summary:
Using verify_area() [or access_ok()] is redundant if copy*user(),
get_user(), or put_user() is being used, but must (*should*) be used
if __copy*user(), __get_user(), or __put_user() are being used.

a.  [include/asm-i386/uaccess.h] verify_area: - Obsolete, use access_ok()

b.  copy_*_user() already calls access_ok() to validate the user address.
    The __* versions of copy*user() and __get/put_user() do not use
    access_ok(), so checking must be done before using them.


HTH.
--
~Randy


| From: Domen Puncer <domen@xxxxxxxxxxxx>
|                                                                               
  
| IMO, that verify_area wasn't needed.
|                                                                               
  
|  linux-260-t5bk12-kj-rddunlap/drivers/net/wireless/orinoco.c |    4
|  ----
|  1 files changed, 4 deletions(-)
|                                                                               
  
| diff -puN drivers/net/wireless/orinoco.c~net_wireless_orinoco_verify
| +drivers/net/wireless/orinoco.c
| ---
| 
+linux-260-t5bk12-kj/drivers/net/wireless/orinoco.c~net_wireless_orinoco_verify
| +2003-09-25 16:03:17.000000000 -0700
| +++ linux-260-t5bk12-kj-rddunlap/drivers/net/wireless/orinoco.c
| 2003-09-25
| +16:03:17.000000000 -0700
| @@ -3833,10 +3833,6 @@ orinoco_ioctl(struct net_device *dev, st
|                                 { SIOCIWLASTPRIV, 0, 0, "dump_recs" },
|                         };
|                                                                               
  
| -                       err = verify_area(VERIFY_WRITE,
| wrq->u.data.pointer,
| +sizeof(privtab));
| -                       if (err)
| -                               break;
| -
|                         wrq->u.data.length = sizeof(privtab) /
| +sizeof(privtab[0]);
|                         if (copy_to_user(wrq->u.data.pointer, privtab,
| +sizeof(privtab)))
|                                 err = -EFAULT;

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