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Groups > linux.kernel > #1326939 > unrolled thread

[PATCH] tty: use __GFP_NOWARN for user-controlled kmalloc()

Started byDmitry Vyukov <dvyukov@google.com>
First post2016-02-04 17:00 +0100
Last post2016-02-05 11:40 +0100
Articles 7 — 4 participants

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  [PATCH] tty: use __GFP_NOWARN for user-controlled kmalloc() Dmitry Vyukov <dvyukov@google.com> - 2016-02-04 17:00 +0100
    Re: [PATCH] tty: use __GFP_NOWARN for user-controlled kmalloc() Peter Hurley <peter@hurleysoftware.com> - 2016-02-04 19:00 +0100
      [PATCH] tty: use __GFP_NOWARN for user-controlled kmalloc Dmitry Vyukov <dvyukov@google.com> - 2016-02-04 19:30 +0100
        Re: [PATCH] tty: use __GFP_NOWARN for user-controlled kmalloc David Rientjes <rientjes@google.com> - 2016-02-04 23:20 +0100
          Re: [PATCH] tty: use __GFP_NOWARN for user-controlled kmalloc Dmitry Vyukov <dvyukov@google.com> - 2016-02-05 08:10 +0100
            Re: [PATCH] tty: use __GFP_NOWARN for user-controlled kmalloc One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-02-05 11:40 +0100
            Re: [PATCH] tty: use __GFP_NOWARN for user-controlled kmalloc David Rientjes <rientjes@google.com> - 2016-02-05 11:40 +0100

#1326939 — [PATCH] tty: use __GFP_NOWARN for user-controlled kmalloc()

FromDmitry Vyukov <dvyukov@google.com>
Date2016-02-04 17:00 +0100
Subject[PATCH] tty: use __GFP_NOWARN for user-controlled kmalloc()
Message-ID<qYuu5-3V9-7@gated-at.bofh.it>
Size of kmalloc() in vc_do_resize() is controlled by user.
Too large kmalloc() size triggers WARNING message on console.

Use __GFP_NOWARN for this kmalloc() to not scare admins.

Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
---
Example WARNING:

WARNING: CPU: 3 PID: 7642 at mm/page_alloc.c:2999
__alloc_pages_nodemask+0x7d2/0x1760()
Modules linked in:
CPU: 3 PID: 7642 Comm: a.out Not tainted 4.4.0+ #276
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
 00000000ffffffff ffff88006d24f610 ffffffff82999e2d 0000000000000000
 ffff880060d9af80 ffffffff86475560 ffff88006d24f650 ffffffff81352089
 ffffffff816721e2 ffffffff86475560 0000000000000bb7 00000000024240c0
Call Trace:
 [<     inline     >] __dump_stack lib/dump_stack.c:15
 [<ffffffff82999e2d>] dump_stack+0x6f/0xa2 lib/dump_stack.c:50
 [<ffffffff81352089>] warn_slowpath_common+0xd9/0x140 kernel/panic.c:482
 [<ffffffff813522b9>] warn_slowpath_null+0x29/0x30 kernel/panic.c:515
 [<     inline     >] __alloc_pages_slowpath mm/page_alloc.c:2999
 [<ffffffff816721e2>] __alloc_pages_nodemask+0x7d2/0x1760 mm/page_alloc.c:3253
 [<ffffffff8174a799>] alloc_pages_current+0xe9/0x450 mm/mempolicy.c:2090
 [<     inline     >] alloc_pages include/linux/gfp.h:459
 [<ffffffff8166df66>] alloc_kmem_pages+0x16/0x100 mm/page_alloc.c:3433
 [<ffffffff816c698f>] kmalloc_order+0x1f/0x80 mm/slab_common.c:1008
 [<ffffffff816c6a0f>] kmalloc_order_trace+0x1f/0x140 mm/slab_common.c:1019
 [<     inline     >] kmalloc_large include/linux/slab.h:395
 [<ffffffff8175b624>] __kmalloc+0x2f4/0x340 mm/slub.c:3557
 [<     inline     >] kmalloc include/linux/slab.h:468
 [<ffffffff82d47800>] vc_do_resize+0x2c0/0x1140 drivers/tty/vt/vt.c:874
 [<ffffffff82d4878a>] vt_resize+0xaa/0xe0 drivers/tty/vt/vt.c:993
 [<     inline     >] tiocswinsz drivers/tty/tty_io.c:2357
 [<ffffffff82cf22b3>] tty_ioctl+0x1083/0x2160 drivers/tty/tty_io.c:2869
 [<     inline     >] vfs_ioctl fs/ioctl.c:43
 [<ffffffff817efdac>] do_vfs_ioctl+0x18c/0xfb0 fs/ioctl.c:674
 [<     inline     >] SYSC_ioctl fs/ioctl.c:689
 [<ffffffff817f0c5f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:680
---
 drivers/tty/vt/vt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index bd51bdd..2382810 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -871,7 +871,7 @@ static int vc_do_resize(struct tty_struct *tty, struct vc_data *vc,
 	if (new_cols == vc->vc_cols && new_rows == vc->vc_rows)
 		return 0;
 
-	newscreen = kmalloc(new_screen_size, GFP_USER);
+	newscreen = kmalloc(new_screen_size, GFP_USER | __GFP_NOWARN);
 	if (!newscreen)
 		return -ENOMEM;
 
-- 
2.7.0.rc3.207.g0ac5344

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#1327078

FromPeter Hurley <peter@hurleysoftware.com>
Date2016-02-04 19:00 +0100
Message-ID<qYwmf-5e9-23@gated-at.bofh.it>
In reply to#1326939
Hi Dmitry,

Just a quick procedural note: tty patches need to be addressed to Greg.


On 02/04/2016 07:55 AM, Dmitry Vyukov wrote:
> Size of kmalloc() in vc_do_resize() is controlled by user.
> Too large kmalloc() size triggers WARNING message on console.
> 
> Use __GFP_NOWARN for this kmalloc() to not scare admins.
> 
> Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
> ---
> Example WARNING:
> 
> WARNING: CPU: 3 PID: 7642 at mm/page_alloc.c:2999
> __alloc_pages_nodemask+0x7d2/0x1760()
> Modules linked in:
> CPU: 3 PID: 7642 Comm: a.out Not tainted 4.4.0+ #276
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>  00000000ffffffff ffff88006d24f610 ffffffff82999e2d 0000000000000000
>  ffff880060d9af80 ffffffff86475560 ffff88006d24f650 ffffffff81352089
>  ffffffff816721e2 ffffffff86475560 0000000000000bb7 00000000024240c0
> Call Trace:
>  [<     inline     >] __dump_stack lib/dump_stack.c:15
>  [<ffffffff82999e2d>] dump_stack+0x6f/0xa2 lib/dump_stack.c:50
>  [<ffffffff81352089>] warn_slowpath_common+0xd9/0x140 kernel/panic.c:482
>  [<ffffffff813522b9>] warn_slowpath_null+0x29/0x30 kernel/panic.c:515
>  [<     inline     >] __alloc_pages_slowpath mm/page_alloc.c:2999
>  [<ffffffff816721e2>] __alloc_pages_nodemask+0x7d2/0x1760 mm/page_alloc.c:3253
>  [<ffffffff8174a799>] alloc_pages_current+0xe9/0x450 mm/mempolicy.c:2090
>  [<     inline     >] alloc_pages include/linux/gfp.h:459
>  [<ffffffff8166df66>] alloc_kmem_pages+0x16/0x100 mm/page_alloc.c:3433
>  [<ffffffff816c698f>] kmalloc_order+0x1f/0x80 mm/slab_common.c:1008
>  [<ffffffff816c6a0f>] kmalloc_order_trace+0x1f/0x140 mm/slab_common.c:1019
>  [<     inline     >] kmalloc_large include/linux/slab.h:395
>  [<ffffffff8175b624>] __kmalloc+0x2f4/0x340 mm/slub.c:3557
>  [<     inline     >] kmalloc include/linux/slab.h:468
>  [<ffffffff82d47800>] vc_do_resize+0x2c0/0x1140 drivers/tty/vt/vt.c:874
>  [<ffffffff82d4878a>] vt_resize+0xaa/0xe0 drivers/tty/vt/vt.c:993
>  [<     inline     >] tiocswinsz drivers/tty/tty_io.c:2357
>  [<ffffffff82cf22b3>] tty_ioctl+0x1083/0x2160 drivers/tty/tty_io.c:2869
>  [<     inline     >] vfs_ioctl fs/ioctl.c:43
>  [<ffffffff817efdac>] do_vfs_ioctl+0x18c/0xfb0 fs/ioctl.c:674
>  [<     inline     >] SYSC_ioctl fs/ioctl.c:689
>  [<ffffffff817f0c5f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:680
> ---
>  drivers/tty/vt/vt.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
> index bd51bdd..2382810 100644
> --- a/drivers/tty/vt/vt.c
> +++ b/drivers/tty/vt/vt.c
> @@ -871,7 +871,7 @@ static int vc_do_resize(struct tty_struct *tty, struct vc_data *vc,
>  	if (new_cols == vc->vc_cols && new_rows == vc->vc_rows)
>  		return 0;
>  
> -	newscreen = kmalloc(new_screen_size, GFP_USER);
> +	newscreen = kmalloc(new_screen_size, GFP_USER | __GFP_NOWARN);
>  	if (!newscreen)
>  		return -ENOMEM;
>  
>

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#1327091 — [PATCH] tty: use __GFP_NOWARN for user-controlled kmalloc

FromDmitry Vyukov <dvyukov@google.com>
Date2016-02-04 19:30 +0100
Subject[PATCH] tty: use __GFP_NOWARN for user-controlled kmalloc
Message-ID<qYwPg-5Eq-19@gated-at.bofh.it>
In reply to#1327078
Size of kmalloc() in vc_do_resize() is controlled by user.
Too large kmalloc() size triggers WARNING message on console.

Use __GFP_NOWARN for this kmalloc() to not scare admins.

Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
---
Example WARNING:

WARNING: CPU: 3 PID: 7642 at mm/page_alloc.c:2999
__alloc_pages_nodemask+0x7d2/0x1760()
Modules linked in:
CPU: 3 PID: 7642 Comm: a.out Not tainted 4.4.0+ #276
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
 00000000ffffffff ffff88006d24f610 ffffffff82999e2d 0000000000000000
 ffff880060d9af80 ffffffff86475560 ffff88006d24f650 ffffffff81352089
 ffffffff816721e2 ffffffff86475560 0000000000000bb7 00000000024240c0
Call Trace:
 [<     inline     >] __dump_stack lib/dump_stack.c:15
 [<ffffffff82999e2d>] dump_stack+0x6f/0xa2 lib/dump_stack.c:50
 [<ffffffff81352089>] warn_slowpath_common+0xd9/0x140 kernel/panic.c:482
 [<ffffffff813522b9>] warn_slowpath_null+0x29/0x30 kernel/panic.c:515
 [<     inline     >] __alloc_pages_slowpath mm/page_alloc.c:2999
 [<ffffffff816721e2>] __alloc_pages_nodemask+0x7d2/0x1760 mm/page_alloc.c:3253
 [<ffffffff8174a799>] alloc_pages_current+0xe9/0x450 mm/mempolicy.c:2090
 [<     inline     >] alloc_pages include/linux/gfp.h:459
 [<ffffffff8166df66>] alloc_kmem_pages+0x16/0x100 mm/page_alloc.c:3433
 [<ffffffff816c698f>] kmalloc_order+0x1f/0x80 mm/slab_common.c:1008
 [<ffffffff816c6a0f>] kmalloc_order_trace+0x1f/0x140 mm/slab_common.c:1019
 [<     inline     >] kmalloc_large include/linux/slab.h:395
 [<ffffffff8175b624>] __kmalloc+0x2f4/0x340 mm/slub.c:3557
 [<     inline     >] kmalloc include/linux/slab.h:468
 [<ffffffff82d47800>] vc_do_resize+0x2c0/0x1140 drivers/tty/vt/vt.c:874
 [<ffffffff82d4878a>] vt_resize+0xaa/0xe0 drivers/tty/vt/vt.c:993
 [<     inline     >] tiocswinsz drivers/tty/tty_io.c:2357
 [<ffffffff82cf22b3>] tty_ioctl+0x1083/0x2160 drivers/tty/tty_io.c:2869
 [<     inline     >] vfs_ioctl fs/ioctl.c:43
 [<ffffffff817efdac>] do_vfs_ioctl+0x18c/0xfb0 fs/ioctl.c:674
 [<     inline     >] SYSC_ioctl fs/ioctl.c:689
 [<ffffffff817f0c5f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:680
---
 drivers/tty/vt/vt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index bd51bdd..2382810 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -871,7 +871,7 @@ static int vc_do_resize(struct tty_struct *tty, struct vc_data *vc,
 	if (new_cols == vc->vc_cols && new_rows == vc->vc_rows)
 		return 0;
 
-	newscreen = kmalloc(new_screen_size, GFP_USER);
+	newscreen = kmalloc(new_screen_size, GFP_USER | __GFP_NOWARN);
 	if (!newscreen)
 		return -ENOMEM;
 
-- 
2.7.0.rc3.207.g0ac5344

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#1327228 — Re: [PATCH] tty: use __GFP_NOWARN for user-controlled kmalloc

FromDavid Rientjes <rientjes@google.com>
Date2016-02-04 23:20 +0100
SubjectRe: [PATCH] tty: use __GFP_NOWARN for user-controlled kmalloc
Message-ID<qYApP-887-3@gated-at.bofh.it>
In reply to#1327091
On Thu, 4 Feb 2016, Dmitry Vyukov wrote:

> Size of kmalloc() in vc_do_resize() is controlled by user.
> Too large kmalloc() size triggers WARNING message on console.
> 
> Use __GFP_NOWARN for this kmalloc() to not scare admins.
> 

Hmm, this is hitting the WARN_ON_ONCE(!(gfp_mask & __GFP_NOWARN)) for 
order >= MAX_ORDER.

vc_do_resize() has

	if (cols > VC_RESIZE_MAXCOL || lines > VC_RESIZE_MAXROW)
		return -EINVAL;

so the appropriate fix would seem to be to reject sizes that would exceed 
the page allocator's ability to return contiguous memory (MAX_ORDER) 
rather than ever trying the allocation in the first place.

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#1327508 — Re: [PATCH] tty: use __GFP_NOWARN for user-controlled kmalloc

FromDmitry Vyukov <dvyukov@google.com>
Date2016-02-05 08:10 +0100
SubjectRe: [PATCH] tty: use __GFP_NOWARN for user-controlled kmalloc
Message-ID<qYIGK-5pB-1@gated-at.bofh.it>
In reply to#1327228
On Thu, Feb 4, 2016 at 11:11 PM, David Rientjes <rientjes@google.com> wrote:
> On Thu, 4 Feb 2016, Dmitry Vyukov wrote:
>
>> Size of kmalloc() in vc_do_resize() is controlled by user.
>> Too large kmalloc() size triggers WARNING message on console.
>>
>> Use __GFP_NOWARN for this kmalloc() to not scare admins.
>>
>
> Hmm, this is hitting the WARN_ON_ONCE(!(gfp_mask & __GFP_NOWARN)) for
> order >= MAX_ORDER.
>
> vc_do_resize() has
>
>         if (cols > VC_RESIZE_MAXCOL || lines > VC_RESIZE_MAXROW)
>                 return -EINVAL;
>
> so the appropriate fix would seem to be to reject sizes that would exceed
> the page allocator's ability to return contiguous memory (MAX_ORDER)
> rather than ever trying the allocation in the first place.

Hi David,

Please see Alan response to original report here:
https://groups.google.com/d/msg/syzkaller/ufjvr5j0URo/lTlpYP0DBQAJ
I can't say that I fully understand it.

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#1327597 — Re: [PATCH] tty: use __GFP_NOWARN for user-controlled kmalloc

FromOne Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Date2016-02-05 11:40 +0100
SubjectRe: [PATCH] tty: use __GFP_NOWARN for user-controlled kmalloc
Message-ID<qYLXX-7pz-5@gated-at.bofh.it>
In reply to#1327508
On Fri, 5 Feb 2016 08:06:12 +0100
Dmitry Vyukov <dvyukov@google.com> wrote:

> On Thu, Feb 4, 2016 at 11:11 PM, David Rientjes <rientjes@google.com> wrote:
> > On Thu, 4 Feb 2016, Dmitry Vyukov wrote:
> >  
> >> Size of kmalloc() in vc_do_resize() is controlled by user.
> >> Too large kmalloc() size triggers WARNING message on console.
> >>
> >> Use __GFP_NOWARN for this kmalloc() to not scare admins.
> >>  
> >
> > Hmm, this is hitting the WARN_ON_ONCE(!(gfp_mask & __GFP_NOWARN)) for
> > order >= MAX_ORDER.
> >
> > vc_do_resize() has
> >
> >         if (cols > VC_RESIZE_MAXCOL || lines > VC_RESIZE_MAXROW)
> >                 return -EINVAL;
> >
> > so the appropriate fix would seem to be to reject sizes that would exceed
> > the page allocator's ability to return contiguous memory (MAX_ORDER)
> > rather than ever trying the allocation in the first place.  
> 
> Hi David,
> 
> Please see Alan response to original report here:
> https://groups.google.com/d/msg/syzkaller/ufjvr5j0URo/lTlpYP0DBQAJ
> I can't say that I fully understand it.

I think we can go down to something like cols * lines < 4MB with complete
safety.

Alan

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#1327599 — Re: [PATCH] tty: use __GFP_NOWARN for user-controlled kmalloc

FromDavid Rientjes <rientjes@google.com>
Date2016-02-05 11:40 +0100
SubjectRe: [PATCH] tty: use __GFP_NOWARN for user-controlled kmalloc
Message-ID<qYLXX-7pz-11@gated-at.bofh.it>
In reply to#1327508
On Fri, 5 Feb 2016, Dmitry Vyukov wrote:

> On Thu, Feb 4, 2016 at 11:11 PM, David Rientjes <rientjes@google.com> wrote:
> > On Thu, 4 Feb 2016, Dmitry Vyukov wrote:
> >
> >> Size of kmalloc() in vc_do_resize() is controlled by user.
> >> Too large kmalloc() size triggers WARNING message on console.
> >>
> >> Use __GFP_NOWARN for this kmalloc() to not scare admins.
> >>
> >
> > Hmm, this is hitting the WARN_ON_ONCE(!(gfp_mask & __GFP_NOWARN)) for
> > order >= MAX_ORDER.
> >
> > vc_do_resize() has
> >
> >         if (cols > VC_RESIZE_MAXCOL || lines > VC_RESIZE_MAXROW)
> >                 return -EINVAL;
> >
> > so the appropriate fix would seem to be to reject sizes that would exceed
> > the page allocator's ability to return contiguous memory (MAX_ORDER)
> > rather than ever trying the allocation in the first place.
> 
> Hi David,
> 
> Please see Alan response to original report here:
> https://groups.google.com/d/msg/syzkaller/ufjvr5j0URo/lTlpYP0DBQAJ
> I can't say that I fully understand it.
> 

vc_do_resize() might not know a stricter limit, but we know the limit that 
the page allocator can provide, and that's MAX_ORDER-1.  kmalloc() with a 
size >= (1 << (PAGE_SHIFT + MAX_ORDER)) will always fail, so if that is 
really the upper limit, then so be it.  We should return -EINVAL 
appropriately and not -ENOMEM.

I'm thinking that the actual limit would actually be 
(1 << (PAGE_SHIFT + pageblock_order)) since even memory compaction isn't 
going to be able to defragment more than that, but the absolute max would 
always be MAX_ORDER-1.

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