* Re: [PATCH] mm: Prevent mapping slab pages to userspace
@ 2019-01-25 18:44 ` Kees Cook
0 siblings, 0 replies; 12+ messages in thread
From: Kees Cook @ 2019-01-25 18:44 UTC (permalink / raw)
To: Matthew Wilcox
Cc: Andrew Morton, Linux-MM, LKML, Rik van Riel, Christoph Lameter,
Pekka Enberg, David Rientjes, Joonsoo Kim, Kernel Hardening,
Michael Ellerman
On Sat, Jan 26, 2019 at 6:38 AM Matthew Wilcox <willy@infradead.org> wrote:
>
> It's never appropriate to map a page allocated by SLAB into userspace.
> A buggy device driver might try this, or an attacker might be able to
> find a way to make it happen.
>
> Signed-off-by: Matthew Wilcox <willy@infradead.org>
> ---
> mm/memory.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index e11ca9dd823f..ce8c90b752be 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1451,7 +1451,7 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr,
> spinlock_t *ptl;
>
> retval = -EINVAL;
> - if (PageAnon(page))
> + if (PageAnon(page) || PageSlab(page))
Are there other types that should not get mapped? (Or better yet, is
there a whitelist of those that are okay to be mapped?)
Either way, this sounds good. :)
Reviewed-by: Kees Cook <keescook@chromium.org>
-Kees
> goto out;
> retval = -ENOMEM;
> flush_dcache_page(page);
> --
> 2.20.1
>
--
Kees Cook
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] mm: Prevent mapping slab pages to userspace
@ 2019-01-25 18:44 ` Kees Cook
0 siblings, 0 replies; 12+ messages in thread
From: Kees Cook @ 2019-01-25 18:44 UTC (permalink / raw)
To: Matthew Wilcox
Cc: Andrew Morton, Linux-MM, LKML, Rik van Riel, Christoph Lameter,
Pekka Enberg, David Rientjes, Joonsoo Kim, Kernel Hardening,
Michael Ellerman
On Sat, Jan 26, 2019 at 6:38 AM Matthew Wilcox <willy@infradead.org> wrote:
>
> It's never appropriate to map a page allocated by SLAB into userspace.
> A buggy device driver might try this, or an attacker might be able to
> find a way to make it happen.
>
> Signed-off-by: Matthew Wilcox <willy@infradead.org>
> ---
> mm/memory.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index e11ca9dd823f..ce8c90b752be 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1451,7 +1451,7 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr,
> spinlock_t *ptl;
>
> retval = -EINVAL;
> - if (PageAnon(page))
> + if (PageAnon(page) || PageSlab(page))
Are there other types that should not get mapped? (Or better yet, is
there a whitelist of those that are okay to be mapped?)
Either way, this sounds good. :)
Reviewed-by: Kees Cook <keescook@chromium.org>
-Kees
> goto out;
> retval = -ENOMEM;
> flush_dcache_page(page);
> --
> 2.20.1
>
--
Kees Cook
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] mm: Prevent mapping slab pages to userspace
2019-01-25 18:44 ` Kees Cook
(?)
@ 2019-01-25 19:30 ` Matthew Wilcox
-1 siblings, 0 replies; 12+ messages in thread
From: Matthew Wilcox @ 2019-01-25 19:30 UTC (permalink / raw)
To: Kees Cook
Cc: Andrew Morton, Linux-MM, LKML, Rik van Riel, Christoph Lameter,
Pekka Enberg, David Rientjes, Joonsoo Kim, Kernel Hardening,
Michael Ellerman
On Sat, Jan 26, 2019 at 07:44:40AM +1300, Kees Cook wrote:
> > - if (PageAnon(page))
> > + if (PageAnon(page) || PageSlab(page))
>
> Are there other types that should not get mapped? (Or better yet, is
> there a whitelist of those that are okay to be mapped?)
Funny you should ask; I think the next patch in this series looks like this:
- if (PageAnon(page) || PageSlab(page))
+ if (PageAnon(page) || PageSlab(page) || page_has_type(page))
but let's see if there's something I've overlooked with this patch.
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] mm: Prevent mapping slab pages to userspace
2019-01-25 17:38 [PATCH] mm: Prevent mapping slab pages to userspace Matthew Wilcox
2019-01-25 18:44 ` Kees Cook
@ 2019-01-28 18:20 ` Andrew Morton
2019-01-28 19:00 ` Kees Cook
2019-01-31 0:37 ` Michael Ellerman
2019-01-31 6:03 ` Pekka Enberg
3 siblings, 1 reply; 12+ messages in thread
From: Andrew Morton @ 2019-01-28 18:20 UTC (permalink / raw)
To: Matthew Wilcox
Cc: linux-mm, linux-kernel, Rik van Riel, Christoph Lameter,
Pekka Enberg, David Rientjes, Joonsoo Kim, kernel-hardening,
Kees Cook, Michael Ellerman
On Fri, 25 Jan 2019 09:38:27 -0800 Matthew Wilcox <willy@infradead.org> wrote:
> It's never appropriate to map a page allocated by SLAB into userspace.
> A buggy device driver might try this, or an attacker might be able to
> find a way to make it happen.
It wouldn't surprise me if someone somewhere is doing this. Rather
than mysteriously breaking their code, how about we emit a warning and
still permit it to proceed, for a while?
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] mm: Prevent mapping slab pages to userspace
2019-01-28 18:20 ` Andrew Morton
@ 2019-01-28 19:00 ` Kees Cook
0 siblings, 0 replies; 12+ messages in thread
From: Kees Cook @ 2019-01-28 19:00 UTC (permalink / raw)
To: Andrew Morton
Cc: Matthew Wilcox, Linux-MM, LKML, Rik van Riel, Christoph Lameter,
Pekka Enberg, David Rientjes, Joonsoo Kim, Kernel Hardening,
Michael Ellerman
On Tue, Jan 29, 2019 at 7:21 AM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Fri, 25 Jan 2019 09:38:27 -0800 Matthew Wilcox <willy@infradead.org> wrote:
>
> > It's never appropriate to map a page allocated by SLAB into userspace.
> > A buggy device driver might try this, or an attacker might be able to
> > find a way to make it happen.
>
> It wouldn't surprise me if someone somewhere is doing this. Rather
> than mysteriously breaking their code, how about we emit a warning and
> still permit it to proceed, for a while?
It seems like a fatal condition to me? There's nothing to check that
such a page wouldn't get freed by the slab while still mapped to
userspace, right?
But I'll take warning over not checking. :)
--
Kees Cook
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] mm: Prevent mapping slab pages to userspace
@ 2019-01-28 19:00 ` Kees Cook
0 siblings, 0 replies; 12+ messages in thread
From: Kees Cook @ 2019-01-28 19:00 UTC (permalink / raw)
To: Andrew Morton
Cc: Matthew Wilcox, Linux-MM, LKML, Rik van Riel, Christoph Lameter,
Pekka Enberg, David Rientjes, Joonsoo Kim, Kernel Hardening,
Michael Ellerman
On Tue, Jan 29, 2019 at 7:21 AM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Fri, 25 Jan 2019 09:38:27 -0800 Matthew Wilcox <willy@infradead.org> wrote:
>
> > It's never appropriate to map a page allocated by SLAB into userspace.
> > A buggy device driver might try this, or an attacker might be able to
> > find a way to make it happen.
>
> It wouldn't surprise me if someone somewhere is doing this. Rather
> than mysteriously breaking their code, how about we emit a warning and
> still permit it to proceed, for a while?
It seems like a fatal condition to me? There's nothing to check that
such a page wouldn't get freed by the slab while still mapped to
userspace, right?
But I'll take warning over not checking. :)
--
Kees Cook
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] mm: Prevent mapping slab pages to userspace
2019-01-28 19:00 ` Kees Cook
@ 2019-01-28 20:08 ` Christopher Lameter
-1 siblings, 0 replies; 12+ messages in thread
From: Christopher Lameter @ 2019-01-28 20:08 UTC (permalink / raw)
To: Kees Cook
Cc: Andrew Morton, Matthew Wilcox, Linux-MM, LKML, Rik van Riel,
Pekka Enberg, David Rientjes, Joonsoo Kim, Kernel Hardening,
Michael Ellerman
On Tue, 29 Jan 2019, Kees Cook wrote:
> It seems like a fatal condition to me? There's nothing to check that
> such a page wouldn't get freed by the slab while still mapped to
> userspace, right?
Lets just fail the code. Currently this may work with SLUB. But SLAB and
SLOB overlay fields with mapcount. So you would have a corrupted page
struct if you mapped a slab page to user space.
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] mm: Prevent mapping slab pages to userspace
@ 2019-01-28 20:08 ` Christopher Lameter
0 siblings, 0 replies; 12+ messages in thread
From: Christopher Lameter @ 2019-01-28 20:08 UTC (permalink / raw)
To: Kees Cook
Cc: Andrew Morton, Matthew Wilcox, Linux-MM, LKML, Rik van Riel,
Pekka Enberg, David Rientjes, Joonsoo Kim, Kernel Hardening,
Michael Ellerman
On Tue, 29 Jan 2019, Kees Cook wrote:
> It seems like a fatal condition to me? There's nothing to check that
> such a page wouldn't get freed by the slab while still mapped to
> userspace, right?
Lets just fail the code. Currently this may work with SLUB. But SLAB and
SLOB overlay fields with mapcount. So you would have a corrupted page
struct if you mapped a slab page to user space.
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] mm: Prevent mapping slab pages to userspace
2019-01-25 17:38 [PATCH] mm: Prevent mapping slab pages to userspace Matthew Wilcox
@ 2019-01-31 0:37 ` Michael Ellerman
2019-01-28 18:20 ` Andrew Morton
` (2 subsequent siblings)
3 siblings, 0 replies; 12+ messages in thread
From: Michael Ellerman @ 2019-01-31 0:37 UTC (permalink / raw)
To: Matthew Wilcox, Andrew Morton
Cc: Matthew Wilcox, linux-mm, linux-kernel, Rik van Riel,
Christoph Lameter, Pekka Enberg, David Rientjes, Joonsoo Kim,
kernel-hardening, Kees Cook
Matthew Wilcox <willy@infradead.org> writes:
> It's never appropriate to map a page allocated by SLAB into userspace.
> A buggy device driver might try this, or an attacker might be able to
> find a way to make it happen.
>
> Signed-off-by: Matthew Wilcox <willy@infradead.org>
> ---
> mm/memory.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index e11ca9dd823f..ce8c90b752be 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1451,7 +1451,7 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr,
> spinlock_t *ptl;
>
> retval = -EINVAL;
> - if (PageAnon(page))
> + if (PageAnon(page) || PageSlab(page))
> goto out;
> retval = -ENOMEM;
> flush_dcache_page(page);
Thanks for turning this into an actual patch.
cheers
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] mm: Prevent mapping slab pages to userspace
@ 2019-01-31 0:37 ` Michael Ellerman
0 siblings, 0 replies; 12+ messages in thread
From: Michael Ellerman @ 2019-01-31 0:37 UTC (permalink / raw)
To: Matthew Wilcox, Andrew Morton
Cc: linux-mm, linux-kernel, Rik van Riel, Christoph Lameter,
Pekka Enberg, David Rientjes, Joonsoo Kim, kernel-hardening,
Kees Cook
Matthew Wilcox <willy@infradead.org> writes:
> It's never appropriate to map a page allocated by SLAB into userspace.
> A buggy device driver might try this, or an attacker might be able to
> find a way to make it happen.
>
> Signed-off-by: Matthew Wilcox <willy@infradead.org>
> ---
> mm/memory.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index e11ca9dd823f..ce8c90b752be 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1451,7 +1451,7 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr,
> spinlock_t *ptl;
>
> retval = -EINVAL;
> - if (PageAnon(page))
> + if (PageAnon(page) || PageSlab(page))
> goto out;
> retval = -ENOMEM;
> flush_dcache_page(page);
Thanks for turning this into an actual patch.
cheers
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] mm: Prevent mapping slab pages to userspace
2019-01-25 17:38 [PATCH] mm: Prevent mapping slab pages to userspace Matthew Wilcox
` (2 preceding siblings ...)
2019-01-31 0:37 ` Michael Ellerman
@ 2019-01-31 6:03 ` Pekka Enberg
3 siblings, 0 replies; 12+ messages in thread
From: Pekka Enberg @ 2019-01-31 6:03 UTC (permalink / raw)
To: Matthew Wilcox, Andrew Morton
Cc: linux-mm, linux-kernel, Rik van Riel, Christoph Lameter,
Pekka Enberg, David Rientjes, Joonsoo Kim, kernel-hardening,
Kees Cook, Michael Ellerman
On 25/01/2019 19.38, Matthew Wilcox wrote:
> It's never appropriate to map a page allocated by SLAB into userspace.
> A buggy device driver might try this, or an attacker might be able to
> find a way to make it happen.
>
> Signed-off-by: Matthew Wilcox <willy@infradead.org>
Acked-by: Pekka Enberg <penberg@kernel.org>
A WARN_ON_ONCE() would be nice here to let those buggy drivers know that
they will no longer work.
> ---
> mm/memory.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index e11ca9dd823f..ce8c90b752be 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1451,7 +1451,7 @@ static int insert_page(struct vm_area_struct *vma, unsigned long addr,
> spinlock_t *ptl;
>
> retval = -EINVAL;
> - if (PageAnon(page))
> + if (PageAnon(page) || PageSlab(page))
> goto out;
> retval = -ENOMEM;
> flush_dcache_page(page);
>
^ permalink raw reply [flat|nested] 12+ messages in thread