* [PATCH] mm/slab: Do not hash pointers when debugging slab
@ 2017-12-07 10:17 Geert Uytterhoeven
2017-12-07 11:13 ` Christopher Lameter
2017-12-10 20:45 ` Linus Torvalds
0 siblings, 2 replies; 7+ messages in thread
From: Geert Uytterhoeven @ 2017-12-07 10:17 UTC (permalink / raw)
To: Christoph Lameter, Pekka Enberg, David Rientjes, Joonsoo Kim,
Andrew Morton
Cc: Tobin C . Harding, linux-mm, linux-kernel, Geert Uytterhoeven
If CONFIG_DEBUG_SLAB/CONFIG_DEBUG_SLAB_LEAK are enabled, the slab code
prints extra debug information when e.g. corruption is detected.
This includes pointers, which are not very useful when hashed.
Fix this by using %px to print unhashed pointers instead.
Fixes: ad67b74d2469d9b8 ("printk: hash addresses printed with %p")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
It's been ages I needed the above options. But of course I need them
just after the introduction of address hashing...
---
mm/slab.c | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)
diff --git a/mm/slab.c b/mm/slab.c
index 183e996dde5ff37a..70be5823227dcb3e 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1585,7 +1585,7 @@ static void print_objinfo(struct kmem_cache *cachep, void *objp, int lines)
}
if (cachep->flags & SLAB_STORE_USER) {
- pr_err("Last user: [<%p>](%pSR)\n",
+ pr_err("Last user: [<%px>](%pSR)\n",
*dbg_userword(cachep, objp),
*dbg_userword(cachep, objp));
}
@@ -1621,7 +1621,7 @@ static void check_poison_obj(struct kmem_cache *cachep, void *objp)
/* Mismatch ! */
/* Print header */
if (lines == 0) {
- pr_err("Slab corruption (%s): %s start=%p, len=%d\n",
+ pr_err("Slab corruption (%s): %s start=%px, len=%d\n",
print_tainted(), cachep->name,
realobj, size);
print_objinfo(cachep, objp, 0);
@@ -1650,13 +1650,13 @@ static void check_poison_obj(struct kmem_cache *cachep, void *objp)
if (objnr) {
objp = index_to_obj(cachep, page, objnr - 1);
realobj = (char *)objp + obj_offset(cachep);
- pr_err("Prev obj: start=%p, len=%d\n", realobj, size);
+ pr_err("Prev obj: start=%px, len=%d\n", realobj, size);
print_objinfo(cachep, objp, 2);
}
if (objnr + 1 < cachep->num) {
objp = index_to_obj(cachep, page, objnr + 1);
realobj = (char *)objp + obj_offset(cachep);
- pr_err("Next obj: start=%p, len=%d\n", realobj, size);
+ pr_err("Next obj: start=%px, len=%d\n", realobj, size);
print_objinfo(cachep, objp, 2);
}
}
@@ -2608,7 +2608,7 @@ static void slab_put_obj(struct kmem_cache *cachep,
/* Verify double free bug */
for (i = page->active; i < cachep->num; i++) {
if (get_free_obj(page, i) == objnr) {
- pr_err("slab: double free detected in cache '%s', objp %p\n",
+ pr_err("slab: double free detected in cache '%s', objp %px\n",
cachep->name, objp);
BUG();
}
@@ -2772,7 +2772,7 @@ static inline void verify_redzone_free(struct kmem_cache *cache, void *obj)
else
slab_error(cache, "memory outside object was overwritten");
- pr_err("%p: redzone 1:0x%llx, redzone 2:0x%llx\n",
+ pr_err("%px: redzone 1:0x%llx, redzone 2:0x%llx\n",
obj, redzone1, redzone2);
}
@@ -3078,7 +3078,7 @@ static void *cache_alloc_debugcheck_after(struct kmem_cache *cachep,
if (*dbg_redzone1(cachep, objp) != RED_INACTIVE ||
*dbg_redzone2(cachep, objp) != RED_INACTIVE) {
slab_error(cachep, "double free, or memory outside object was overwritten");
- pr_err("%p: redzone 1:0x%llx, redzone 2:0x%llx\n",
+ pr_err("%px: redzone 1:0x%llx, redzone 2:0x%llx\n",
objp, *dbg_redzone1(cachep, objp),
*dbg_redzone2(cachep, objp));
}
@@ -3091,7 +3091,7 @@ static void *cache_alloc_debugcheck_after(struct kmem_cache *cachep,
cachep->ctor(objp);
if (ARCH_SLAB_MINALIGN &&
((unsigned long)objp & (ARCH_SLAB_MINALIGN-1))) {
- pr_err("0x%p: not aligned to ARCH_SLAB_MINALIGN=%d\n",
+ pr_err("0x%px: not aligned to ARCH_SLAB_MINALIGN=%d\n",
objp, (int)ARCH_SLAB_MINALIGN);
}
return objp;
@@ -4283,7 +4283,7 @@ static void show_symbol(struct seq_file *m, unsigned long address)
return;
}
#endif
- seq_printf(m, "%p", (void *)address);
+ seq_printf(m, "%px", (void *)address);
}
static int leaks_show(struct seq_file *m, void *p)
--
2.7.4
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH] mm/slab: Do not hash pointers when debugging slab
2017-12-07 10:17 [PATCH] mm/slab: Do not hash pointers when debugging slab Geert Uytterhoeven
@ 2017-12-07 11:13 ` Christopher Lameter
2017-12-07 18:43 ` Kees Cook
2017-12-10 20:45 ` Linus Torvalds
1 sibling, 1 reply; 7+ messages in thread
From: Christopher Lameter @ 2017-12-07 11:13 UTC (permalink / raw)
To: Geert Uytterhoeven
Cc: Pekka Enberg, David Rientjes, Joonsoo Kim, Andrew Morton,
Tobin C . Harding, linux-mm, linux-kernel, Kees Cook
On Thu, 7 Dec 2017, Geert Uytterhoeven wrote:
> If CONFIG_DEBUG_SLAB/CONFIG_DEBUG_SLAB_LEAK are enabled, the slab code
> prints extra debug information when e.g. corruption is detected.
> This includes pointers, which are not very useful when hashed.
>
> Fix this by using %px to print unhashed pointers instead.
Acked-by: Christoph Lameter <cl@linux.com>
These SLAB config options are only used for testing so this is ok.
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^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] mm/slab: Do not hash pointers when debugging slab
2017-12-07 11:13 ` Christopher Lameter
@ 2017-12-07 18:43 ` Kees Cook
2017-12-07 20:15 ` Christopher Lameter
0 siblings, 1 reply; 7+ messages in thread
From: Kees Cook @ 2017-12-07 18:43 UTC (permalink / raw)
To: Christopher Lameter
Cc: Geert Uytterhoeven, Pekka Enberg, David Rientjes, Joonsoo Kim,
Andrew Morton, Tobin C . Harding, Linux-MM, LKML, Linus Torvalds
On Thu, Dec 7, 2017 at 3:13 AM, Christopher Lameter <cl@linux.com> wrote:
> On Thu, 7 Dec 2017, Geert Uytterhoeven wrote:
>
>> If CONFIG_DEBUG_SLAB/CONFIG_DEBUG_SLAB_LEAK are enabled, the slab code
>> prints extra debug information when e.g. corruption is detected.
>> This includes pointers, which are not very useful when hashed.
>>
>> Fix this by using %px to print unhashed pointers instead.
>
> Acked-by: Christoph Lameter <cl@linux.com>
>
> These SLAB config options are only used for testing so this is ok.
Most systems use SLUB so I can't say how common CONFIG_DEBUG_SLAB is.
(Though, FWIW with SLUB, CONFIG_SLUB_DEBUG is very common.)
-Kees
--
Kees Cook
Pixel Security
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^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] mm/slab: Do not hash pointers when debugging slab
2017-12-07 18:43 ` Kees Cook
@ 2017-12-07 20:15 ` Christopher Lameter
0 siblings, 0 replies; 7+ messages in thread
From: Christopher Lameter @ 2017-12-07 20:15 UTC (permalink / raw)
To: Kees Cook
Cc: Geert Uytterhoeven, Pekka Enberg, David Rientjes, Joonsoo Kim,
Andrew Morton, Tobin C . Harding, Linux-MM, LKML, Linus Torvalds
On Thu, 7 Dec 2017, Kees Cook wrote:
> > These SLAB config options are only used for testing so this is ok.
>
> Most systems use SLUB so I can't say how common CONFIG_DEBUG_SLAB is.
> (Though, FWIW with SLUB, CONFIG_SLUB_DEBUG is very common.)
CONFIG_SLUB_DEBUG is on by default because it compiles into the kernel the
runtime configurable debugging framework. It does not activate any
debugging.
CONFIG_SLUB_DEBUG_ON is the equivalent to CONFIG_SLAB_DEBUG. The kernel
will boot with debugging on without any extra kernel options with these.
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^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] mm/slab: Do not hash pointers when debugging slab
2017-12-07 10:17 [PATCH] mm/slab: Do not hash pointers when debugging slab Geert Uytterhoeven
2017-12-07 11:13 ` Christopher Lameter
@ 2017-12-10 20:45 ` Linus Torvalds
2017-12-11 8:08 ` Geert Uytterhoeven
2017-12-11 12:00 ` Christopher Lameter
1 sibling, 2 replies; 7+ messages in thread
From: Linus Torvalds @ 2017-12-10 20:45 UTC (permalink / raw)
To: Geert Uytterhoeven
Cc: Christoph Lameter, Pekka Enberg, David Rientjes, Joonsoo Kim,
Andrew Morton, Tobin C . Harding, linux-mm,
Linux Kernel Mailing List
On Thu, Dec 7, 2017 at 2:17 AM, Geert Uytterhoeven
<geert+renesas@glider.be> wrote:
>
> if (cachep->flags & SLAB_STORE_USER) {
> - pr_err("Last user: [<%p>](%pSR)\n",
> + pr_err("Last user: [<%px>](%pSR)\n",
> *dbg_userword(cachep, objp),
> *dbg_userword(cachep, objp));
Is there actually any point to the %px at all?
Why not remove it? the _real_ information is printed out by %pSR, and
that's both sufficient and useful in ways %px isn't.
> - pr_err("Slab corruption (%s): %s start=%p, len=%d\n",
> + pr_err("Slab corruption (%s): %s start=%px, len=%d\n",
> print_tainted(), cachep->name,
> realobj, size);
and here, is the pointer actually interesting, or should we just give
the offset to the allocation?
But if the pointer is interesting, then ack.
Linus
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^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] mm/slab: Do not hash pointers when debugging slab
2017-12-10 20:45 ` Linus Torvalds
@ 2017-12-11 8:08 ` Geert Uytterhoeven
2017-12-11 12:00 ` Christopher Lameter
1 sibling, 0 replies; 7+ messages in thread
From: Geert Uytterhoeven @ 2017-12-11 8:08 UTC (permalink / raw)
To: Linus Torvalds
Cc: Geert Uytterhoeven, Christoph Lameter, Pekka Enberg,
David Rientjes, Joonsoo Kim, Andrew Morton, Tobin C . Harding,
linux-mm, Linux Kernel Mailing List
Hi Linus,
On Sun, Dec 10, 2017 at 9:45 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Thu, Dec 7, 2017 at 2:17 AM, Geert Uytterhoeven
> <geert+renesas@glider.be> wrote:
>> - pr_err("Slab corruption (%s): %s start=%p, len=%d\n",
>> + pr_err("Slab corruption (%s): %s start=%px, len=%d\n",
>> print_tainted(), cachep->name,
>> realobj, size);
>
> and here, is the pointer actually interesting, or should we just give
> the offset to the allocation?
The pointer may help to identify e.g. an empty list_head in the written data.
> But if the pointer is interesting, then ack.
Thanks!
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] mm/slab: Do not hash pointers when debugging slab
2017-12-10 20:45 ` Linus Torvalds
2017-12-11 8:08 ` Geert Uytterhoeven
@ 2017-12-11 12:00 ` Christopher Lameter
1 sibling, 0 replies; 7+ messages in thread
From: Christopher Lameter @ 2017-12-11 12:00 UTC (permalink / raw)
To: Linus Torvalds
Cc: Geert Uytterhoeven, Pekka Enberg, David Rientjes, Joonsoo Kim,
Andrew Morton, Tobin C . Harding, linux-mm,
Linux Kernel Mailing List
On Sun, 10 Dec 2017, Linus Torvalds wrote:
> On Thu, Dec 7, 2017 at 2:17 AM, Geert Uytterhoeven
> <geert+renesas@glider.be> wrote:
> >
> > if (cachep->flags & SLAB_STORE_USER) {
> > - pr_err("Last user: [<%p>](%pSR)\n",
> > + pr_err("Last user: [<%px>](%pSR)\n",
> > *dbg_userword(cachep, objp),
> > *dbg_userword(cachep, objp));
>
> Is there actually any point to the %px at all?
>
> Why not remove it? the _real_ information is printed out by %pSR, and
> that's both sufficient and useful in ways %px isn't.
This pointer refers to code so we can remove it.
>
> > - pr_err("Slab corruption (%s): %s start=%p, len=%d\n",
> > + pr_err("Slab corruption (%s): %s start=%px, len=%d\n",
> > print_tainted(), cachep->name,
> > realobj, size);
>
> and here, is the pointer actually interesting, or should we just give
> the offset to the allocation?
>
> But if the pointer is interesting, then ack.
The pointer here is to an slab object which could be important if one
wants to find the pointer value in a hexdump of another object (f.e.
listhead) or other pointer information that is being inspected
in a debugging session.
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2017-12-07 10:17 [PATCH] mm/slab: Do not hash pointers when debugging slab Geert Uytterhoeven
2017-12-07 11:13 ` Christopher Lameter
2017-12-07 18:43 ` Kees Cook
2017-12-07 20:15 ` Christopher Lameter
2017-12-10 20:45 ` Linus Torvalds
2017-12-11 8:08 ` Geert Uytterhoeven
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