* [PATCH] mm: slub: fix conversion of freelist_corrupted()
@ 2020-08-11 12:46 Eugeniu Rosca
2020-08-11 20:49 ` Andrew Morton
2020-08-14 6:57 ` Dongli Zhang
0 siblings, 2 replies; 6+ messages in thread
From: Eugeniu Rosca @ 2020-08-11 12:46 UTC (permalink / raw)
To: Andrew Morton, Dongli Zhang
Cc: linux-mm, stable, Eugeniu Rosca, Eugeniu Rosca
Commit 52f23478081ae0 ("mm/slub.c: fix corrupted freechain in
deactivate_slab()") suffered an update when picked up from LKML [1].
Specifically, relocating 'freelist = NULL' into 'freelist_corrupted()'
created a no-op statement. Fix it by sticking to the behavior intended
in the original patch [1]. Prefer the lowest-line-count solution.
[1] https://lore.kernel.org/linux-mm/20200331031450.12182-1-dongli.zhang@oracle.com/
Fixes: 52f23478081ae0 ("mm/slub.c: fix corrupted freechain in deactivate_slab()")
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dongli Zhang <dongli.zhang@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
---
mm/slub.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c
index 68c02b2eecd9..9a3e963b02a3 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -677,7 +677,6 @@ static bool freelist_corrupted(struct kmem_cache *s, struct page *page,
if ((s->flags & SLAB_CONSISTENCY_CHECKS) &&
!check_valid_pointer(s, page, nextfree)) {
object_err(s, page, freelist, "Freechain corrupt");
- freelist = NULL;
slab_fix(s, "Isolate corrupted freechain");
return true;
}
@@ -2184,8 +2183,10 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page,
* 'freelist' is already corrupted. So isolate all objects
* starting at 'freelist'.
*/
- if (freelist_corrupted(s, page, freelist, nextfree))
+ if (freelist_corrupted(s, page, freelist, nextfree)) {
+ freelist = NULL;
break;
+ }
do {
prior = page->freelist;
--
2.28.0
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH] mm: slub: fix conversion of freelist_corrupted()
2020-08-11 12:46 [PATCH] mm: slub: fix conversion of freelist_corrupted() Eugeniu Rosca
@ 2020-08-11 20:49 ` Andrew Morton
2020-08-12 9:06 ` Eugeniu Rosca
2020-08-14 6:57 ` Dongli Zhang
1 sibling, 1 reply; 6+ messages in thread
From: Andrew Morton @ 2020-08-11 20:49 UTC (permalink / raw)
To: Eugeniu Rosca; +Cc: Dongli Zhang, linux-mm, stable, Eugeniu Rosca
On Tue, 11 Aug 2020 14:46:56 +0200 Eugeniu Rosca <erosca@de.adit-jv.com> wrote:
> Commit 52f23478081ae0 ("mm/slub.c: fix corrupted freechain in
> deactivate_slab()") suffered an update when picked up from LKML [1].
>
> Specifically, relocating 'freelist = NULL' into 'freelist_corrupted()'
> created a no-op statement. Fix it by sticking to the behavior intended
> in the original patch [1]. Prefer the lowest-line-count solution.
>
> [1] https://lore.kernel.org/linux-mm/20200331031450.12182-1-dongli.zhang@oracle.com/
>
> ...
>
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -677,7 +677,6 @@ static bool freelist_corrupted(struct kmem_cache *s, struct page *page,
> if ((s->flags & SLAB_CONSISTENCY_CHECKS) &&
> !check_valid_pointer(s, page, nextfree)) {
> object_err(s, page, freelist, "Freechain corrupt");
> - freelist = NULL;
> slab_fix(s, "Isolate corrupted freechain");
> return true;
> }
> @@ -2184,8 +2183,10 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page,
> * 'freelist' is already corrupted. So isolate all objects
> * starting at 'freelist'.
> */
> - if (freelist_corrupted(s, page, freelist, nextfree))
> + if (freelist_corrupted(s, page, freelist, nextfree)) {
> + freelist = NULL;
> break;
> + }
>
> do {
> prior = page->freelist;
Looks right.
What are the runtime effects of this change? In other words, what are
the end user visible effects of the present defect?
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] mm: slub: fix conversion of freelist_corrupted()
2020-08-11 20:49 ` Andrew Morton
@ 2020-08-12 9:06 ` Eugeniu Rosca
0 siblings, 0 replies; 6+ messages in thread
From: Eugeniu Rosca @ 2020-08-12 9:06 UTC (permalink / raw)
To: Andrew Morton
Cc: Eugeniu Rosca, Dongli Zhang, linux-mm, stable, Eugeniu Rosca
Dear Andrew,
On Tue, Aug 11, 2020 at 01:49:09PM -0700, Andrew Morton wrote:
> On Tue, 11 Aug 2020 14:46:56 +0200 Eugeniu Rosca <erosca@de.adit-jv.com> wrote:
>
> > Commit 52f23478081ae0 ("mm/slub.c: fix corrupted freechain in
> > deactivate_slab()") suffered an update when picked up from LKML [1].
> >
> > Specifically, relocating 'freelist = NULL' into 'freelist_corrupted()'
> > created a no-op statement. Fix it by sticking to the behavior intended
> > in the original patch [1]. Prefer the lowest-line-count solution.
> >
> > [1] https://lore.kernel.org/linux-mm/20200331031450.12182-1-dongli.zhang@oracle.com/
> >
> > ...
> >
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -677,7 +677,6 @@ static bool freelist_corrupted(struct kmem_cache *s, struct page *page,
> > if ((s->flags & SLAB_CONSISTENCY_CHECKS) &&
> > !check_valid_pointer(s, page, nextfree)) {
> > object_err(s, page, freelist, "Freechain corrupt");
> > - freelist = NULL;
> > slab_fix(s, "Isolate corrupted freechain");
> > return true;
> > }
> > @@ -2184,8 +2183,10 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page,
> > * 'freelist' is already corrupted. So isolate all objects
> > * starting at 'freelist'.
> > */
> > - if (freelist_corrupted(s, page, freelist, nextfree))
> > + if (freelist_corrupted(s, page, freelist, nextfree)) {
> > + freelist = NULL;
> > break;
> > + }
> >
> > do {
> > prior = page->freelist;
>
> Looks right.
>
> What are the runtime effects of this change? In other words, what are
> the end user visible effects of the present defect?
Thank you for the prompt feedback.
The issue popped up as a result of static analysis and code review.
Therefore, I lack any specific runtime behavior example being fixed.
Nevertheless, I think this does not diminish the concern expressed in
the description of the patch.
--
Best regards,
Eugeniu Rosca
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] mm: slub: fix conversion of freelist_corrupted()
2020-08-11 12:46 [PATCH] mm: slub: fix conversion of freelist_corrupted() Eugeniu Rosca
2020-08-11 20:49 ` Andrew Morton
@ 2020-08-14 6:57 ` Dongli Zhang
2020-08-14 7:46 ` Eugeniu Rosca
1 sibling, 1 reply; 6+ messages in thread
From: Dongli Zhang @ 2020-08-14 6:57 UTC (permalink / raw)
To: Eugeniu Rosca, Andrew Morton; +Cc: linux-mm, stable, Eugeniu Rosca
On 8/11/20 5:46 AM, Eugeniu Rosca wrote:
> Commit 52f23478081ae0 ("mm/slub.c: fix corrupted freechain in
> deactivate_slab()") suffered an update when picked up from LKML [1].
>
> Specifically, relocating 'freelist = NULL' into 'freelist_corrupted()'
> created a no-op statement. Fix it by sticking to the behavior intended
> in the original patch [1]. Prefer the lowest-line-count solution.
>
> [1] https://lore.kernel.org/linux-mm/20200331031450.12182-1-dongli.zhang@oracle.com/
>
> Fixes: 52f23478081ae0 ("mm/slub.c: fix corrupted freechain in deactivate_slab()")
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Dongli Zhang <dongli.zhang@oracle.com>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
> ---
> mm/slub.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index 68c02b2eecd9..9a3e963b02a3 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -677,7 +677,6 @@ static bool freelist_corrupted(struct kmem_cache *s, struct page *page,
> if ((s->flags & SLAB_CONSISTENCY_CHECKS) &&
> !check_valid_pointer(s, page, nextfree)) {
> object_err(s, page, freelist, "Freechain corrupt");
> - freelist = NULL;
> slab_fix(s, "Isolate corrupted freechain");
> return true;
> }
> @@ -2184,8 +2183,10 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page,
> * 'freelist' is already corrupted. So isolate all objects
> * starting at 'freelist'.
> */
> - if (freelist_corrupted(s, page, freelist, nextfree))
> + if (freelist_corrupted(s, page, freelist, nextfree)) {
> + freelist = NULL;
This is good to me.
However, this would confuse people when CONFIG_SLUB_DEBUG is not defined.
While reading the source code, people may be curious why to reset freelist when
CONFIG_SLUB_DEBUG is even not defined.
Dongli Zhang
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] mm: slub: fix conversion of freelist_corrupted()
2020-08-14 6:57 ` Dongli Zhang
@ 2020-08-14 7:46 ` Eugeniu Rosca
2020-08-14 19:43 ` Dongli Zhang
0 siblings, 1 reply; 6+ messages in thread
From: Eugeniu Rosca @ 2020-08-14 7:46 UTC (permalink / raw)
To: Dongli Zhang
Cc: Eugeniu Rosca, Andrew Morton, linux-mm, stable, Eugeniu Rosca
Hello Dongli,
On Thu, Aug 13, 2020 at 11:57:51PM -0700, Dongli Zhang wrote:
> On 8/11/20 5:46 AM, Eugeniu Rosca wrote:
> > Commit 52f23478081ae0 ("mm/slub.c: fix corrupted freechain in
> > deactivate_slab()") suffered an update when picked up from LKML [1].
> >
> > Specifically, relocating 'freelist = NULL' into 'freelist_corrupted()'
> > created a no-op statement. Fix it by sticking to the behavior intended
> > in the original patch [1]. Prefer the lowest-line-count solution.
> >
> > [1] https://lore.kernel.org/linux-mm/20200331031450.12182-1-dongli.zhang@oracle.com/
> >
> > Fixes: 52f23478081ae0 ("mm/slub.c: fix corrupted freechain in deactivate_slab()")
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: Dongli Zhang <dongli.zhang@oracle.com>
> > Cc: <stable@vger.kernel.org>
> > Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
> > ---
> > mm/slub.c | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/mm/slub.c b/mm/slub.c
> > index 68c02b2eecd9..9a3e963b02a3 100644
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -677,7 +677,6 @@ static bool freelist_corrupted(struct kmem_cache *s, struct page *page,
> > if ((s->flags & SLAB_CONSISTENCY_CHECKS) &&
> > !check_valid_pointer(s, page, nextfree)) {
> > object_err(s, page, freelist, "Freechain corrupt");
> > - freelist = NULL;
> > slab_fix(s, "Isolate corrupted freechain");
> > return true;
> > }
> > @@ -2184,8 +2183,10 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page,
> > * 'freelist' is already corrupted. So isolate all objects
> > * starting at 'freelist'.
> > */
> > - if (freelist_corrupted(s, page, freelist, nextfree))
> > + if (freelist_corrupted(s, page, freelist, nextfree)) {
> > + freelist = NULL;
>
> This is good to me.
>
> However, this would confuse people when CONFIG_SLUB_DEBUG is not defined.
>
> While reading the source code, people may be curious why to reset freelist when
> CONFIG_SLUB_DEBUG is even not defined.
This is a fair point. To address it, the `freelist = NULL` assignment
should be then moved into the body of freelist_corrupted(). If no
concerns on that, I will soon push a v2 implementing this proposal.
--
Best regards,
Eugeniu Rosca
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] mm: slub: fix conversion of freelist_corrupted()
2020-08-14 7:46 ` Eugeniu Rosca
@ 2020-08-14 19:43 ` Dongli Zhang
0 siblings, 0 replies; 6+ messages in thread
From: Dongli Zhang @ 2020-08-14 19:43 UTC (permalink / raw)
To: Eugeniu Rosca; +Cc: Andrew Morton, linux-mm, stable, Eugeniu Rosca
On 8/14/20 12:46 AM, Eugeniu Rosca wrote:
> Hello Dongli,
>
> On Thu, Aug 13, 2020 at 11:57:51PM -0700, Dongli Zhang wrote:
>> On 8/11/20 5:46 AM, Eugeniu Rosca wrote:
>>> Commit 52f23478081ae0 ("mm/slub.c: fix corrupted freechain in
>>> deactivate_slab()") suffered an update when picked up from LKML [1].
>>>
>>> Specifically, relocating 'freelist = NULL' into 'freelist_corrupted()'
>>> created a no-op statement. Fix it by sticking to the behavior intended
>>> in the original patch [1]. Prefer the lowest-line-count solution.
>>>
>>> [1] https://urldefense.com/v3/__https://lore.kernel.org/linux-mm/20200331031450.12182-1-dongli.zhang@oracle.com/__;!!GqivPVa7Brio!LkxH4qJ3WzKnO_nmONLWV-HAougEaefnp8UnI6qC_8j0SS9_9fkO6bOe68flixlQzx8$
>>>
>>> Fixes: 52f23478081ae0 ("mm/slub.c: fix corrupted freechain in deactivate_slab()")
>>> Cc: Andrew Morton <akpm@linux-foundation.org>
>>> Cc: Dongli Zhang <dongli.zhang@oracle.com>
>>> Cc: <stable@vger.kernel.org>
>>> Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
>>> ---
>>> mm/slub.c | 5 +++--
>>> 1 file changed, 3 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/mm/slub.c b/mm/slub.c
>>> index 68c02b2eecd9..9a3e963b02a3 100644
>>> --- a/mm/slub.c
>>> +++ b/mm/slub.c
>>> @@ -677,7 +677,6 @@ static bool freelist_corrupted(struct kmem_cache *s, struct page *page,
>>> if ((s->flags & SLAB_CONSISTENCY_CHECKS) &&
>>> !check_valid_pointer(s, page, nextfree)) {
>>> object_err(s, page, freelist, "Freechain corrupt");
>>> - freelist = NULL;
>>> slab_fix(s, "Isolate corrupted freechain");
>>> return true;
>>> }
>>> @@ -2184,8 +2183,10 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page,
>>> * 'freelist' is already corrupted. So isolate all objects
>>> * starting at 'freelist'.
>>> */
>>> - if (freelist_corrupted(s, page, freelist, nextfree))
>>> + if (freelist_corrupted(s, page, freelist, nextfree)) {
>>> + freelist = NULL;
>>
>> This is good to me.
>>
>> However, this would confuse people when CONFIG_SLUB_DEBUG is not defined.
>>
>> While reading the source code, people may be curious why to reset freelist when
>> CONFIG_SLUB_DEBUG is even not defined.
>
> This is a fair point. To address it, the `freelist = NULL` assignment
> should be then moved into the body of freelist_corrupted(). If no
> concerns on that, I will soon push a v2 implementing this proposal.
>
I do have have concern with that if that can make both of static analysis tool
and the people reading code happy :)
Thank you very much!
Dongli Zhang
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2020-08-14 19:43 UTC | newest]
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2020-08-11 12:46 [PATCH] mm: slub: fix conversion of freelist_corrupted() Eugeniu Rosca
2020-08-11 20:49 ` Andrew Morton
2020-08-12 9:06 ` Eugeniu Rosca
2020-08-14 6:57 ` Dongli Zhang
2020-08-14 7:46 ` Eugeniu Rosca
2020-08-14 19:43 ` Dongli Zhang
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