kernel 2.6.24.1 still vulnerable to the vmsplice local root exploit

kernel 2.6.24.1 still vulnerable to the vmsplice local root exploit

[Niki Denev]

Hi,

As the subject says the 2.6.24.1 is still vulnerable to the vmsplice
local root exploit.

[opa@test tmp]$ uname -a
Linux tester 2.6.24.1 #1 Sun Feb 10 00:06:49 EST 2008 i686 unknown
[opa@test tmp]$ ./vms

-----------------------------------
 Linux vmsplice Local Root Exploit
 By qaaz
-----------------------------------
[+] mmap: 0x0 .. 0x1000
[+] page: 0x0
[+] page: 0x20
[+] mmap: 0x4000 .. 0x5000
[+] page: 0x4000
[+] page: 0x4020
[+] mmap: 0x1000 .. 0x2000
[+] page: 0x1000
[+] mmap: 0xb7f56000 .. 0xb7f88000
[+] root
[root@test tmp]#
[root@test tmp]# id
uid=0(root) gid=0(root) groups=2033(opa)
[root@test tmp]# uname -a
Linux test 2.6.24.1 #1 Sun Feb 10 00:06:49 EST 2008 i686 unknown

Is there any known fix/patch for this?

Re: kernel 2.6.24.1 still vulnerable to the vmsplice local root exploit

[Willy Tarreau]

On Sun, Feb 10, 2008 at 08:04:35AM +0200, Niki Denev wrote:
> Hi,
> 
> As the subject says the 2.6.24.1 is still vulnerable to the vmsplice
> local root exploit.

Yes indeed, that's quite bad. 2.6.24-git is still vulnerable too, and
also contains the fix :-(

CC'd Jens as he worked on the fix.

Willy

Re: kernel 2.6.24.1 still vulnerable to the vmsplice local root exploit

[Niki Denev]

On Feb 10, 2008 8:32 AM, Willy Tarreau <w@1wt.eu> wrote:
> On Sun, Feb 10, 2008 at 08:04:35AM +0200, Niki Denev wrote:
> > Hi,
> >
> > As the subject says the 2.6.24.1 is still vulnerable to the vmsplice
> > local root exploit.
>
> Yes indeed, that's quite bad. 2.6.24-git is still vulnerable too, and
> also contains the fix :-(
>
> CC'd Jens as he worked on the fix.
>
> Willy
>
>

I was unable to gain root on 2.6.24-git20
but after several segfaults when executing the exploit continously
the machine crashes.

--Niki

Re: [PATCH] kernel 2.6.24.1 still vulnerable to the vmsplice local root exploit

[Niki Denev]

On Feb 10, 2008 1:38 AM, Niki Denev <ndenev@gmail.com> wrote:
>
> On Feb 10, 2008 8:32 AM, Willy Tarreau <w@1wt.eu> wrote:
> > On Sun, Feb 10, 2008 at 08:04:35AM +0200, Niki Denev wrote:
> > > Hi,
> > >
> > > As the subject says the 2.6.24.1 is still vulnerable to the vmsplice
> > > local root exploit.
> >
> > Yes indeed, that's quite bad. 2.6.24-git is still vulnerable too, and
> > also contains the fix :-(
> >
> > CC'd Jens as he worked on the fix.
> >
> > Willy
> >
> >
>
> I was unable to gain root on 2.6.24-git20
> but after several segfaults when executing the exploit continously
> the machine crashes.
>
> --Niki
>

this fixed the problem for me (kernel 2.6.24.1) :
It appears that the initial patch checked the input to vmsplice_to_user,
but the exploit used vmsplice_to_pipe which remained open to the attack.

--- fs/splice.c.orig	2008-02-08 21:55:30.000000000 +0200
+++ fs/splice.c	2008-02-10 11:32:50.000000000 +0200
@@ -1443,6 +1443,10 @@
 	struct pipe_inode_info *pipe;
 	struct page *pages[PIPE_BUFFERS];
 	struct partial_page partial[PIPE_BUFFERS];
+	int error;
+	long ret;
+	void __user *base;
+	size_t len;
 	struct splice_pipe_desc spd = {
 		.pages = pages,
 		.partial = partial,
@@ -1450,6 +1454,31 @@
 		.ops = &user_page_pipe_buf_ops,
 	};

+	error = ret = 0;
+
+	/*
+	 * Get user address base and length for this iovec.
+	 */
+	error = get_user(base, &iov->iov_base);
+	if (unlikely(error))
+		return error;
+	error = get_user(len, &iov->iov_len);
+	if (unlikely(error))
+		return error;
+
+	/*
+	 * Sanity check this iovec. 0 read succeeds.
+	 */
+	if (unlikely(!len))
+		return 0;
+	if (unlikely(!base)) {
+		return -EFAULT;	
+	}
+
+	if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
+		return -EFAULT;
+	}
+
 	pipe = pipe_info(file->f_path.dentry->d_inode);
 	if (!pipe)
 		return -EBADF;

Re: [PATCH] kernel 2.6.24.1 still vulnerable to the vmsplice local root exploit

[Oliver Pinter]

hmmm, with 2.6.22.y serie is too affected

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
Last login: Sat Feb  9 15:34:35 2008
oliver@home:~$ ./2617_26241_root_exploit
-----------------------------------
 Linux vmsplice Local Root Exploit
 By qaaz
-----------------------------------
[+] mmap: 0x0 .. 0x1000
[+] page: 0x0
[+] page: 0x20
[+] mmap: 0x4000 .. 0x5000
[+] page: 0x4000
[+] page: 0x4020
[+] mmap: 0x1000 .. 0x2000
[+] page: 0x1000
[+] mmap: 0xb7f79000 .. 0xb7fab000
[+] root
root@home:~# uname -a
Linux home 2.6.22.17 #3 SMP PREEMPT Mon Feb 4 17:38:33 CET 2008 i686 GNU/Linux
root@home:~#

-- 
Thanks,
Oliver

Re: [PATCH] kernel 2.6.24.1 still vulnerable to the vmsplice local root exploit

[Bastian Blank]

On Sun, Feb 10, 2008 at 04:40:53AM -0500, Niki Denev wrote:
> this fixed the problem for me (kernel 2.6.24.1) :
> It appears that the initial patch checked the input to vmsplice_to_user,
> but the exploit used vmsplice_to_pipe which remained open to the attack.

This patch is broken. It opens the old hole again.

> @@ -1450,6 +1454,31 @@
>  		.ops = &user_page_pipe_buf_ops,
>  	};
> 
> +	error = ret = 0;
> +
> +	/*
> +	 * Get user address base and length for this iovec.
> +	 */
> +	error = get_user(base, &iov->iov_base);
> +	if (unlikely(error))
> +		return error;
> +	error = get_user(len, &iov->iov_len);
> +	if (unlikely(error))
> +		return error;

iov is unchecked.

> +	if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
> +		return -EFAULT;
> +	}

Use VERIFY_READ and this only checks the first entry.

I checked the following patch and it at least fixes the known exploit.

diff --git a/fs/splice.c b/fs/splice.c
index 14e2262..80beb2b 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1237,6 +1237,11 @@ static int get_iovec_page_array(const struct iovec __user *iov,
 		if (unlikely(!base))
 			break;
 
+		if (!access_ok(VERIFY_READ, base, len)) {
+			error = -EFAULT;
+			break;
+		}
+
 		/*
 		 * Get this base offset and number of pages, then map
 		 * in the user pages.
-- 
Even historians fail to learn from history -- they repeat the same mistakes.
		-- John Gill, "Patterns of Force", stardate 2534.7

Re: [PATCH] kernel 2.6.24.1 still vulnerable to the vmsplice local root exploit

[Niki Denev]

On Feb 10, 2008 12:22 PM, Bastian Blank <bastian@waldi.eu.org> wrote:
> On Sun, Feb 10, 2008 at 04:40:53AM -0500, Niki Denev wrote:
> > this fixed the problem for me (kernel 2.6.24.1) :
> > It appears that the initial patch checked the input to vmsplice_to_user,
> > but the exploit used vmsplice_to_pipe which remained open to the attack.
>
> This patch is broken. It opens the old hole again.
>
> > @@ -1450,6 +1454,31 @@
> >               .ops = &user_page_pipe_buf_ops,
> >       };
> >
> > +     error = ret = 0;
> > +
> > +     /*
> > +      * Get user address base and length for this iovec.
> > +      */
> > +     error = get_user(base, &iov->iov_base);
> > +     if (unlikely(error))
> > +             return error;
> > +     error = get_user(len, &iov->iov_len);
> > +     if (unlikely(error))
> > +             return error;
>
> iov is unchecked.
>
> > +     if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
> > +             return -EFAULT;
> > +     }
>
> Use VERIFY_READ and this only checks the first entry.
>
> I checked the following patch and it at least fixes the known exploit.
>
> diff --git a/fs/splice.c b/fs/splice.c
> index 14e2262..80beb2b 100644
> --- a/fs/splice.c
> +++ b/fs/splice.c
> @@ -1237,6 +1237,11 @@ static int get_iovec_page_array(const struct iovec __user *iov,
>                 if (unlikely(!base))
>                         break;
>
> +               if (!access_ok(VERIFY_READ, base, len)) {
> +                       error = -EFAULT;
> +                       break;
> +               }
> +
>                 /*
>                  * Get this base offset and number of pages, then map
>                  * in the user pages.
> --
> Even historians fail to learn from history -- they repeat the same mistakes.
>                 -- John Gill, "Patterns of Force", stardate 2534.7
>

This patch is against 2.6.24.1 which has already the fix to vmsplice_to_user
With it i can't exploit the hole, and it is returns "invalid address"

Re: [PATCH] kernel 2.6.24.1 still vulnerable to the vmsplice local root exploit

[Bastian Blank]

On Sun, Feb 10, 2008 at 12:39:05PM +0000, Niki Denev wrote:
> This patch is against 2.6.24.1 which has already the fix to vmsplice_to_user
> With it i can't exploit the hole, and it is returns "invalid address"

This is the vmsplice_to_pipe path and I have many reports that it is not
fixed.

Bastian

-- 
If there are self-made purgatories, then we all have to live in them.
		-- Spock, "This Side of Paradise", stardate 3417.7

Re: [PATCH] kernel 2.6.24.1 still vulnerable to the vmsplice local root exploit

[Niki Denev]

On Feb 10, 2008 12:47 PM, Bastian Blank <bastian@waldi.eu.org> wrote:
> On Sun, Feb 10, 2008 at 12:39:05PM +0000, Niki Denev wrote:
> > This patch is against 2.6.24.1 which has already the fix to vmsplice_to_user
> > With it i can't exploit the hole, and it is returns "invalid address"
>
> This is the vmsplice_to_pipe path and I have many reports that it is not
> fixed.
>
> Bastian

Exactly, my patch is for the the vmsplice_to_pipe path.
I don't guarantee correctness, but it stops the exploit in my environment.

Niki

Re: [PATCH] kernel 2.6.24.1 still vulnerable to the vmsplice local root exploit

[Oliver Pinter]

thx it fixed for 2.6.22

>>>>>>>

commit f6e993b835393543bab2d917f9dea75218473edd
Author: Oliver Pinter <oliver.pntr@gmail.com>
Date:   Sun Feb 10 14:03:46 2008 +0100

    [PATCH] vm: splice local root exploit fix for 2.6.22.y

    Based on Bastian Blank's patch

    Fix for CVE_2008_0009 and CVE_2008-0010

    ----->8-----

    oliver@pancs:/tmp$ ./2617_26241_root_exploit
    -----------------------------------
     Linux vmsplice Local Root Exploit
      By qaaz
      -----------------------------------
      [+] mmap: 0x0 .. 0x1000
      [+] page: 0x0
      [+] page: 0x20
      [+] mmap: 0x4000 .. 0x5000
      [+] page: 0x4000
      [+] page: 0x4020
      [+] mmap: 0x1000 .. 0x2000
      [+] page: 0x1000
      [+] mmap: 0xb7f1a000 .. 0xb7f4c000
      [-] vmsplice: Bad address

    -----8<-----

    Signed-off-by: Oliver Pinter <oliver.pntr@gmail.com>

diff --git a/fs/splice.c b/fs/splice.c
index e263d3b..d8b106e 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1182,6 +1182,12 @@ static int get_iovec_page_array(const struct
iovec __user *iov,
 		if (unlikely(!base))
 			break;

+		/* CVE-2008-0009, CVE-2008-0010 fix */
+		if(!access_ok(VERIFY_READ, base, len)) {
+			error = -EFAULT;
+			break;
+		}
+
 		/*
 		 * Get this base offset and number of pages, then map
 		 * in the user pages.


<<<<<<<

On 2/10/08, Bastian Blank <bastian@waldi.eu.org> wrote:
> On Sun, Feb 10, 2008 at 12:39:05PM +0000, Niki Denev wrote:
> > This patch is against 2.6.24.1 which has already the fix to
> vmsplice_to_user
> > With it i can't exploit the hole, and it is returns "invalid address"
>
> This is the vmsplice_to_pipe path and I have many reports that it is not
> fixed.
>
> Bastian
>
> --
> If there are self-made purgatories, then we all have to live in them.
> 		-- Spock, "This Side of Paradise", stardate 3417.7
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
>

oliver@pancs:/tmp$ ./2617_26241_root_exploit
-----------------------------------
 Linux vmsplice Local Root Exploit
 By qaaz
-----------------------------------
[+] mmap: 0x0 .. 0x1000
[+] page: 0x0
[+] page: 0x20
[+] mmap: 0x4000 .. 0x5000
[+] page: 0x4000
[+] page: 0x4020
[+] mmap: 0x1000 .. 0x2000
[+] page: 0x1000
[+] mmap: 0xb7f1a000 .. 0xb7f4c000
[-] vmsplice: Bad addres

-- 
Thanks,
Oliver

Re: [stable] [PATCH] kernel 2.6.24.1 still vulnerable to the vmsplice local root exploit

[Greg KH]

On Sun, Feb 10, 2008 at 02:02:27PM +0100, Oliver Pinter wrote:
> thx it fixed for 2.6.22
> 
> >>>>>>>
> 
> commit f6e993b835393543bab2d917f9dea75218473edd
> Author: Oliver Pinter <oliver.pntr@gmail.com>
> Date:   Sun Feb 10 14:03:46 2008 +0100
> 
>     [PATCH] vm: splice local root exploit fix for 2.6.22.y
> 
>     Based on Bastian Blank's patch
> 
>     Fix for CVE_2008_0009 and CVE_2008-0010
> 
>     ----->8-----
> 
>     oliver@pancs:/tmp$ ./2617_26241_root_exploit
>     -----------------------------------
>      Linux vmsplice Local Root Exploit
>       By qaaz
>       -----------------------------------
>       [+] mmap: 0x0 .. 0x1000
>       [+] page: 0x0
>       [+] page: 0x20
>       [+] mmap: 0x4000 .. 0x5000
>       [+] page: 0x4000
>       [+] page: 0x4020
>       [+] mmap: 0x1000 .. 0x2000
>       [+] page: 0x1000
>       [+] mmap: 0xb7f1a000 .. 0xb7f4c000
>       [-] vmsplice: Bad address
> 
>     -----8<-----
> 
>     Signed-off-by: Oliver Pinter <oliver.pntr@gmail.com>
> 
> diff --git a/fs/splice.c b/fs/splice.c
> index e263d3b..d8b106e 100644
> --- a/fs/splice.c
> +++ b/fs/splice.c
> @@ -1182,6 +1182,12 @@ static int get_iovec_page_array(const struct
> iovec __user *iov,
>  		if (unlikely(!base))
>  			break;
> 
> +		/* CVE-2008-0009, CVE-2008-0010 fix */

No, this is a different CVE, as it is a different problem from the
original 09 and 10 report.

It has been given CVE-2008-0600 to address this issue (09 and 10 only
affect .23 and .24 kernels, and have been fixed.)

> +		if(!access_ok(VERIFY_READ, base, len)) {
> +			error = -EFAULT;
> +			break;
> +		}

Hm, perhaps we should just properly check the len field instead?  That's
what is being overflowed here...

thanks,

greg k-h

Re: [stable] [PATCH] kernel 2.6.24.1 still vulnerable to the vmsplice local root exploit

[Pekka Enberg]

On Feb 10, 2008 7:05 PM, Greg KH <greg@kroah.com> wrote:
> No, this is a different CVE, as it is a different problem from the
> original 09 and 10 report.
>
> It has been given CVE-2008-0600 to address this issue (09 and 10 only
> affect .23 and .24 kernels, and have been fixed.)
>
> > +             if(!access_ok(VERIFY_READ, base, len)) {
> > +                     error = -EFAULT;
> > +                     break;
> > +             }
>
> Hm, perhaps we should just properly check the len field instead?  That's
> what is being overflowed here...

Sorry, I forgot to cc you on this one:

http://lkml.org/lkml/2008/2/10/153

I don't see where the current code is checking that base is
accessible. We just check that we can copy the struct iovecs, right?

                        Pekka

Re: [stable] [PATCH] kernel 2.6.24.1 still vulnerable to the vmsplice local root exploit

[Oliver Pinter]

simple len and base check is already in kernel:

2.6.22.17 @ 1176,2-16 - fs/splice.c

                /*
                 * Sanity check this iovec. 0 read succeeds.
                 */
                if (unlikely(!len))
                        break;
                error = -EFAULT;
                if (unlikely(!base))
                        break;



On 2/10/08, Greg KH <greg@kroah.com> wrote:
> On Sun, Feb 10, 2008 at 02:02:27PM +0100, Oliver Pinter wrote:
> > thx it fixed for 2.6.22
> >
> > >>>>>>>
> >
> > commit f6e993b835393543bab2d917f9dea75218473edd
> > Author: Oliver Pinter <oliver.pntr@gmail.com>
> > Date:   Sun Feb 10 14:03:46 2008 +0100
> >
> >     [PATCH] vm: splice local root exploit fix for 2.6.22.y
> >
> >     Based on Bastian Blank's patch
> >
> >     Fix for CVE_2008_0009 and CVE_2008-0010
> >
> >     ----->8-----
> >
> >     oliver@pancs:/tmp$ ./2617_26241_root_exploit
> >     -----------------------------------
> >      Linux vmsplice Local Root Exploit
> >       By qaaz
> >       -----------------------------------
> >       [+] mmap: 0x0 .. 0x1000
> >       [+] page: 0x0
> >       [+] page: 0x20
> >       [+] mmap: 0x4000 .. 0x5000
> >       [+] page: 0x4000
> >       [+] page: 0x4020
> >       [+] mmap: 0x1000 .. 0x2000
> >       [+] page: 0x1000
> >       [+] mmap: 0xb7f1a000 .. 0xb7f4c000
> >       [-] vmsplice: Bad address
> >
> >     -----8<-----
> >
> >     Signed-off-by: Oliver Pinter <oliver.pntr@gmail.com>
> >
> > diff --git a/fs/splice.c b/fs/splice.c
> > index e263d3b..d8b106e 100644
> > --- a/fs/splice.c
> > +++ b/fs/splice.c
> > @@ -1182,6 +1182,12 @@ static int get_iovec_page_array(const struct
> > iovec __user *iov,
> >  		if (unlikely(!base))
> >  			break;
> >
> > +		/* CVE-2008-0009, CVE-2008-0010 fix */
>
> No, this is a different CVE, as it is a different problem from the
> original 09 and 10 report.
>
> It has been given CVE-2008-0600 to address this issue (09 and 10 only
> affect .23 and .24 kernels, and have been fixed.)
>
> > +		if(!access_ok(VERIFY_READ, base, len)) {
> > +			error = -EFAULT;
> > +			break;
> > +		}
>
> Hm, perhaps we should just properly check the len field instead?  That's
> what is being overflowed here...
>
> thanks,
>
> greg k-h
>


-- 
Thanks,
Oliver

Re: [stable] [PATCH] kernel 2.6.24.1 still vulnerable to the vmsplice local root exploit

[Oliver Pinter]

thanks the info

On 2/10/08, Greg KH <greg@kroah.com> wrote:
> On Sun, Feb 10, 2008 at 02:02:27PM +0100, Oliver Pinter wrote:
> > thx it fixed for 2.6.22
> >
> > >>>>>>>
> >
> > commit f6e993b835393543bab2d917f9dea75218473edd
> > Author: Oliver Pinter <oliver.pntr@gmail.com>
> > Date:   Sun Feb 10 14:03:46 2008 +0100
> >
> >     [PATCH] vm: splice local root exploit fix for 2.6.22.y
> >
> >     Based on Bastian Blank's patch
> >
> >     Fix for CVE_2008_0009 and CVE_2008-0010
> >
> >     ----->8-----
> >
> >     oliver@pancs:/tmp$ ./2617_26241_root_exploit
> >     -----------------------------------
> >      Linux vmsplice Local Root Exploit
> >       By qaaz
> >       -----------------------------------
> >       [+] mmap: 0x0 .. 0x1000
> >       [+] page: 0x0
> >       [+] page: 0x20
> >       [+] mmap: 0x4000 .. 0x5000
> >       [+] page: 0x4000
> >       [+] page: 0x4020
> >       [+] mmap: 0x1000 .. 0x2000
> >       [+] page: 0x1000
> >       [+] mmap: 0xb7f1a000 .. 0xb7f4c000
> >       [-] vmsplice: Bad address
> >
> >     -----8<-----
> >
> >     Signed-off-by: Oliver Pinter <oliver.pntr@gmail.com>
> >
> > diff --git a/fs/splice.c b/fs/splice.c
> > index e263d3b..d8b106e 100644
> > --- a/fs/splice.c
> > +++ b/fs/splice.c
> > @@ -1182,6 +1182,12 @@ static int get_iovec_page_array(const struct
> > iovec __user *iov,
> >  		if (unlikely(!base))
> >  			break;
> >
> > +		/* CVE-2008-0009, CVE-2008-0010 fix */
>
> No, this is a different CVE, as it is a different problem from the
> original 09 and 10 report.
>
> It has been given CVE-2008-0600 to address this issue (09 and 10 only
> affect .23 and .24 kernels, and have been fixed.)
>
> > +		if(!access_ok(VERIFY_READ, base, len)) {
> > +			error = -EFAULT;
> > +			break;
> > +		}
>
> Hm, perhaps we should just properly check the len field instead?  That's
> what is being overflowed here...
>
> thanks,
>
> greg k-h
>


-- 
Thanks,
Oliver

Re: [PATCH] kernel 2.6.24.1 still vulnerable to the vmsplice local root exploit

[Niki Denev]

On Feb 10, 2008 12:22 PM, Bastian Blank <bastian@waldi.eu.org> wrote:
> On Sun, Feb 10, 2008 at 04:40:53AM -0500, Niki Denev wrote:
> > this fixed the problem for me (kernel 2.6.24.1) :
> > It appears that the initial patch checked the input to vmsplice_to_user,
> > but the exploit used vmsplice_to_pipe which remained open to the attack.
>
> This patch is broken. It opens the old hole again.
>
> > @@ -1450,6 +1454,31 @@
> >               .ops = &user_page_pipe_buf_ops,
> >       };
> >
> > +     error = ret = 0;
> > +
> > +     /*
> > +      * Get user address base and length for this iovec.
> > +      */
> > +     error = get_user(base, &iov->iov_base);
> > +     if (unlikely(error))
> > +             return error;
> > +     error = get_user(len, &iov->iov_len);
> > +     if (unlikely(error))
> > +             return error;
>
> iov is unchecked.
>
> > +     if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
> > +             return -EFAULT;
> > +     }
>
> Use VERIFY_READ and this only checks the first entry.
>
> I checked the following patch and it at least fixes the known exploit.
>
> diff --git a/fs/splice.c b/fs/splice.c
> index 14e2262..80beb2b 100644
> --- a/fs/splice.c
> +++ b/fs/splice.c
> @@ -1237,6 +1237,11 @@ static int get_iovec_page_array(const struct iovec __user *iov,
>                 if (unlikely(!base))
>                         break;
>
> +               if (!access_ok(VERIFY_READ, base, len)) {
> +                       error = -EFAULT;
> +                       break;
> +               }
> +
>                 /*
>                  * Get this base offset and number of pages, then map
>                  * in the user pages.
> --
> Even historians fail to learn from history -- they repeat the same mistakes.
>                 -- John Gill, "Patterns of Force", stardate 2534.7
>

As far as i can see, at least on x86 and x86_64 the first argument to
access_ok : (VERIFY_READ|VERIFY_WRITE) is ignored.
Also even if it is used on different arch, using WRITE instead of READ
should be safe because WRITE is a superset of READ.

You are right that it only catches the first entry.

--Niki