* [RFC PATCH v2] mm: slub: print kernel addresses in slub debug messages
@ 2019-08-09 1:08 miles.chen
2019-08-09 2:46 ` Matthew Wilcox
0 siblings, 1 reply; 6+ messages in thread
From: miles.chen @ 2019-08-09 1:08 UTC (permalink / raw)
To: Christoph Lameter, Pekka Enberg, David Rientjes, Joonsoo Kim,
Andrew Morton
Cc: linux-mm, linux-kernel, linux-mediatek, wsd_upstream, Miles Chen,
Tobin C . Harding, Kees Cook
From: Miles Chen <miles.chen@mediatek.com>
This RFC patch is sent to discuss the printing address with %p issue.
Since commit ad67b74d2469d9b8 ("printk: hash addresses printed with %p"),
%p gives obfuscated addresses now. When CONFIG_SLUB_DEBUG=y, it is still
useful to get real virtual addresses.
Possible approaches are:
1. stop printing kernel addresses
2. print with %pK,
3. print with %px.
4. do nothing
This patch takes %px approach and shows the output here.
(%px will causes checkpatch warnings, let us ignore the warning here to
have the discussion). Also, use DUMP_PREFIX_OFFSET instead of
DUMP_PREFIX_ADDRESS.
Before this patch:
INFO: Slab 0x(____ptrval____) objects=25 used=10 fp=0x(____ptrval____)
INFO: Object 0x(____ptrval____) @offset=1408 fp=0x(____ptrval____)
Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b a5
Redzone (____ptrval____): bb bb bb bb bb bb bb bb
Padding (____ptrval____): 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
Padding (____ptrval____): 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
Padding (____ptrval____): 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
Padding (____ptrval____): 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
...
FIX kmalloc-128: Object at 0x(____ptrval____) not freed
After this patch:
INFO: Slab 0xffffffbf00f57000 objects=25 used=23 fp=0xffffffc03d5c3500
INFO: Object 0xffffffc03d5c3500 @offset=13568 fp=0xffffffc03d5c0800
Redzone 00000000: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
Redzone 00000010: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
Redzone 00000020: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
Redzone 00000030: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
Redzone 00000040: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
Redzone 00000050: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
Redzone 00000060: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
Redzone 00000070: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
Object 00000000: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object 00000010: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object 00000020: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object 00000030: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object 00000040: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object 00000050: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object 00000060: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object 00000070: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b a5
Redzone 00000000: bb bb bb bb bb bb bb bb
Padding 00000000: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
Padding 00000010: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
Padding 00000020: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
Padding 00000030: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
...
FIX kmalloc-128: Object at 0xffffffc03d5c3500 not freed
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tobin C. Harding <me@tobin.cc>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Miles Chen <miles.chen@mediatek.com>
---
mm/slub.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c
index 8834563cdb4b..bc1fb8e81557 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -528,7 +528,7 @@ static void print_section(char *level, char *text, u8 *addr,
unsigned int length)
{
metadata_access_enable();
- print_hex_dump(level, text, DUMP_PREFIX_ADDRESS, 16, 1, addr,
+ print_hex_dump(level, text, DUMP_PREFIX_OFFSET, 16, 1, addr,
length, 1);
metadata_access_disable();
}
@@ -611,7 +611,7 @@ static void print_tracking(struct kmem_cache *s, void *object)
static void print_page_info(struct page *page)
{
- pr_err("INFO: Slab 0x%p objects=%u used=%u fp=0x%p flags=0x%04lx\n",
+ pr_err("INFO: Slab 0x%px objects=%u used=%u fp=0x%px flags=0x%04lx\n",
page, page->objects, page->inuse, page->freelist, page->flags);
}
@@ -653,7 +653,7 @@ static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p)
print_page_info(page);
- pr_err("INFO: Object 0x%p @offset=%tu fp=0x%p\n\n",
+ pr_err("INFO: Object 0x%px @offset=%tu fp=0x%px\n\n",
p, p - addr, get_freepointer(s, p));
if (s->flags & SLAB_RED_ZONE)
@@ -991,7 +991,7 @@ static void trace(struct kmem_cache *s, struct page *page, void *object,
int alloc)
{
if (s->flags & SLAB_TRACE) {
- pr_info("TRACE %s %s 0x%p inuse=%d fp=0x%p\n",
+ pr_info("TRACE %s %s 0x%px inuse=%d fp=0x%p\n",
s->name,
alloc ? "alloc" : "free",
object, page->inuse,
@@ -1212,7 +1212,7 @@ static noinline int free_debug_processing(
slab_unlock(page);
spin_unlock_irqrestore(&n->list_lock, flags);
if (!ret)
- slab_fix(s, "Object at 0x%p not freed", object);
+ slab_fix(s, "Object at 0x%px not freed", object);
return ret;
}
@@ -3693,7 +3693,7 @@ static void list_slab_objects(struct kmem_cache *s, struct page *page,
for_each_object(p, s, addr, page->objects) {
if (!test_bit(slab_index(p, s, addr), map)) {
- pr_err("INFO: Object 0x%p @offset=%tu\n", p, p - addr);
+ pr_err("INFO: Object 0x%px @offset=%tu\n", p, p - addr);
print_tracking(s, p);
}
}
--
2.18.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [RFC PATCH v2] mm: slub: print kernel addresses in slub debug messages
2019-08-09 1:08 [RFC PATCH v2] mm: slub: print kernel addresses in slub debug messages miles.chen
@ 2019-08-09 2:46 ` Matthew Wilcox
2019-08-09 14:11 ` Miles Chen
2019-08-12 13:32 ` Vlastimil Babka
0 siblings, 2 replies; 6+ messages in thread
From: Matthew Wilcox @ 2019-08-09 2:46 UTC (permalink / raw)
To: miles.chen
Cc: Christoph Lameter, Pekka Enberg, David Rientjes, Joonsoo Kim,
Andrew Morton, linux-mm, linux-kernel, linux-mediatek,
wsd_upstream, Tobin C . Harding, Kees Cook
On Fri, Aug 09, 2019 at 09:08:37AM +0800, miles.chen@mediatek.com wrote:
> Possible approaches are:
> 1. stop printing kernel addresses
> 2. print with %pK,
> 3. print with %px.
No. The point of obscuring kernel addresses is that if the attacker manages to find a way to get the kernel to spit out some debug messages that we shouldn't
leak all this extra information.
> 4. do nothing
5. Find something more useful to print.
> INFO: Slab 0x(____ptrval____) objects=25 used=10 fp=0x(____ptrval____)
... you don't have any randomness on your platform?
> INFO: Object 0x(____ptrval____) @offset=1408 fp=0x(____ptrval____)
> Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
> Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
> Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
> Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
> Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
> Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
> Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
> Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
> Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
> Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
> Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
> Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
> Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
> Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
> Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
> Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b a5
> Redzone (____ptrval____): bb bb bb bb bb bb bb bb
> Padding (____ptrval____): 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
> Padding (____ptrval____): 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
> Padding (____ptrval____): 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
> Padding (____ptrval____): 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
> ...
> FIX kmalloc-128: Object at 0x(____ptrval____) not freed
But if you have randomness, at least some of these "pointers" are valuable
because you can compare them against "pointers" printed by other parts
of the kernel.
> After this patch:
>
> INFO: Slab 0xffffffbf00f57000 objects=25 used=23 fp=0xffffffc03d5c3500
> INFO: Object 0xffffffc03d5c3500 @offset=13568 fp=0xffffffc03d5c0800
> Redzone 00000000: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
> Redzone 00000010: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
> Redzone 00000020: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
> Redzone 00000030: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
> Redzone 00000040: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
> Redzone 00000050: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
> Redzone 00000060: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
> Redzone 00000070: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
> Object 00000000: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
> Object 00000010: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
> Object 00000020: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
> Object 00000030: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
> Object 00000040: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
> Object 00000050: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
> Object 00000060: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
> Object 00000070: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b a5
> Redzone 00000000: bb bb bb bb bb bb bb bb
> Padding 00000000: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
> Padding 00000010: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
> Padding 00000020: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
> Padding 00000030: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
> ...
> FIX kmalloc-128: Object at 0xffffffc03d5c3500 not freed
It looks prettier, but I'm not convinced it's more useful. Unless your
platform lacks randomness ...
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [RFC PATCH v2] mm: slub: print kernel addresses in slub debug messages
2019-08-09 2:46 ` Matthew Wilcox
@ 2019-08-09 14:11 ` Miles Chen
2019-08-09 14:26 ` Matthew Wilcox
2019-08-12 13:32 ` Vlastimil Babka
1 sibling, 1 reply; 6+ messages in thread
From: Miles Chen @ 2019-08-09 14:11 UTC (permalink / raw)
To: Matthew Wilcox
Cc: Christoph Lameter, Pekka Enberg, David Rientjes, Joonsoo Kim,
Andrew Morton, linux-mm, linux-kernel, linux-mediatek,
wsd_upstream, Tobin C . Harding, Kees Cook
On Thu, 2019-08-08 at 19:46 -0700, Matthew Wilcox wrote:
> On Fri, Aug 09, 2019 at 09:08:37AM +0800, miles.chen@mediatek.com wrote:
> > Possible approaches are:
> > 1. stop printing kernel addresses
> > 2. print with %pK,
> > 3. print with %px.
>
> No. The point of obscuring kernel addresses is that if the attacker manages to find a way to get the kernel to spit out some debug messages that we shouldn't
> leak all this extra information.
got it.
>
> > 4. do nothing
>
> 5. Find something more useful to print.
agree
>
> > INFO: Slab 0x(____ptrval____) objects=25 used=10 fp=0x(____ptrval____)
>
> ... you don't have any randomness on your platform?
We have randomized base on our platforms.
> But if you have randomness, at least some of these "pointers" are valuable
> because you can compare them against "pointers" printed by other parts
> of the kernel.
Understood. Keep current %p, do not leak kernel addresses.
I'll collect more cases and see if we really need some extra
information. (maybe the @offset in current message is enough)
thanks for your comments!
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [RFC PATCH v2] mm: slub: print kernel addresses in slub debug messages
2019-08-09 14:11 ` Miles Chen
@ 2019-08-09 14:26 ` Matthew Wilcox
2019-08-12 8:24 ` Miles Chen
0 siblings, 1 reply; 6+ messages in thread
From: Matthew Wilcox @ 2019-08-09 14:26 UTC (permalink / raw)
To: Miles Chen
Cc: Christoph Lameter, Pekka Enberg, David Rientjes, Joonsoo Kim,
Andrew Morton, linux-mm, linux-kernel, linux-mediatek,
wsd_upstream, Tobin C . Harding, Kees Cook
On Fri, Aug 09, 2019 at 10:11:58PM +0800, Miles Chen wrote:
> On Thu, 2019-08-08 at 19:46 -0700, Matthew Wilcox wrote:
> > On Fri, Aug 09, 2019 at 09:08:37AM +0800, miles.chen@mediatek.com wrote:
> > > INFO: Slab 0x(____ptrval____) objects=25 used=10 fp=0x(____ptrval____)
> >
> > ... you don't have any randomness on your platform?
>
> We have randomized base on our platforms.
Look at initialize_ptr_random(). If you have randomness, then you
get a siphash_1u32() of the address. With no randomness, you get this
___ptrval___ string instead.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [RFC PATCH v2] mm: slub: print kernel addresses in slub debug messages
2019-08-09 14:26 ` Matthew Wilcox
@ 2019-08-12 8:24 ` Miles Chen
0 siblings, 0 replies; 6+ messages in thread
From: Miles Chen @ 2019-08-12 8:24 UTC (permalink / raw)
To: Matthew Wilcox
Cc: Christoph Lameter, Pekka Enberg, David Rientjes, Joonsoo Kim,
Andrew Morton, linux-mm, linux-kernel, linux-mediatek,
wsd_upstream, Tobin C . Harding, Kees Cook
On Fri, 2019-08-09 at 07:26 -0700, Matthew Wilcox wrote:
> On Fri, Aug 09, 2019 at 10:11:58PM +0800, Miles Chen wrote:
> > On Thu, 2019-08-08 at 19:46 -0700, Matthew Wilcox wrote:
> > > On Fri, Aug 09, 2019 at 09:08:37AM +0800, miles.chen@mediatek.com wrote:
> > > > INFO: Slab 0x(____ptrval____) objects=25 used=10 fp=0x(____ptrval____)
> > >
> > > ... you don't have any randomness on your platform?
> >
> > We have randomized base on our platforms.
>
> Look at initialize_ptr_random(). If you have randomness, then you
> get a siphash_1u32() of the address. With no randomness, you get this
> ___ptrval___ string instead.
>
You are right. There is no randomness in this platform. (I ran my test
code on Qemu with no randomness)
thanks again
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [RFC PATCH v2] mm: slub: print kernel addresses in slub debug messages
2019-08-09 2:46 ` Matthew Wilcox
2019-08-09 14:11 ` Miles Chen
@ 2019-08-12 13:32 ` Vlastimil Babka
1 sibling, 0 replies; 6+ messages in thread
From: Vlastimil Babka @ 2019-08-12 13:32 UTC (permalink / raw)
To: Matthew Wilcox, miles.chen
Cc: Christoph Lameter, Pekka Enberg, David Rientjes, Joonsoo Kim,
Andrew Morton, linux-mm, linux-kernel, linux-mediatek,
wsd_upstream, Tobin C . Harding, Kees Cook
On 8/9/19 4:46 AM, Matthew Wilcox wrote:
> On Fri, Aug 09, 2019 at 09:08:37AM +0800, miles.chen@mediatek.com wrote:
>> Possible approaches are:
>> 1. stop printing kernel addresses
>> 2. print with %pK,
>> 3. print with %px.
>
> No. The point of obscuring kernel addresses is that if the attacker manages to find a way to get the kernel to spit out some debug messages that we shouldn't
> leak all this extra information.
On the other hand, while CONFIG_SLUB_DEBUG=y is common, the actual
checks and printing happens when the (relatively expensive) checks are
actually enabled during boot, i.e. during a debugging session, not
production defaults. I can see how knowing the exact address might be
useful when e.g. a crash dump is also taken. I would say %pK would be a
good fit, if kptr_restrict also had a setting that makes %pK behave like
%px (looks like it doesn't), so that setting would be enabled in such a
debugging session.
>> 4. do nothing
>
> 5. Find something more useful to print.
>
>> INFO: Slab 0x(____ptrval____) objects=25 used=10 fp=0x(____ptrval____)
>
> ... you don't have any randomness on your platform?
>
>> INFO: Object 0x(____ptrval____) @offset=1408 fp=0x(____ptrval____)
>> Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
>> Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
>> Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
>> Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
>> Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
>> Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
>> Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
>> Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
>> Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
>> Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
>> Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
>> Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
>> Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
>> Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
>> Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
>> Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b a5
>> Redzone (____ptrval____): bb bb bb bb bb bb bb bb
>> Padding (____ptrval____): 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
>> Padding (____ptrval____): 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
>> Padding (____ptrval____): 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
>> Padding (____ptrval____): 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
>> ...
>> FIX kmalloc-128: Object at 0x(____ptrval____) not freed
>
> But if you have randomness, at least some of these "pointers" are valuable
> because you can compare them against "pointers" printed by other parts
> of the kernel.
>
>> After this patch:
>>
>> INFO: Slab 0xffffffbf00f57000 objects=25 used=23 fp=0xffffffc03d5c3500
>> INFO: Object 0xffffffc03d5c3500 @offset=13568 fp=0xffffffc03d5c0800
>> Redzone 00000000: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
>> Redzone 00000010: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
>> Redzone 00000020: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
>> Redzone 00000030: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
>> Redzone 00000040: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
>> Redzone 00000050: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
>> Redzone 00000060: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
>> Redzone 00000070: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
>> Object 00000000: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
>> Object 00000010: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
>> Object 00000020: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
>> Object 00000030: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
>> Object 00000040: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
>> Object 00000050: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
>> Object 00000060: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
>> Object 00000070: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b a5
>> Redzone 00000000: bb bb bb bb bb bb bb bb
>> Padding 00000000: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
>> Padding 00000010: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
>> Padding 00000020: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
>> Padding 00000030: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a
>> ...
>> FIX kmalloc-128: Object at 0xffffffc03d5c3500 not freed
>
> It looks prettier, but I'm not convinced it's more useful. Unless your
> platform lacks randomness ...
>
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2019-08-12 13:32 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-08-09 1:08 [RFC PATCH v2] mm: slub: print kernel addresses in slub debug messages miles.chen
2019-08-09 2:46 ` Matthew Wilcox
2019-08-09 14:11 ` Miles Chen
2019-08-09 14:26 ` Matthew Wilcox
2019-08-12 8:24 ` Miles Chen
2019-08-12 13:32 ` Vlastimil Babka
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