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[PATCH v2] mm/codetag: clear tags before swap

David Wang posted 1 patch 1 year ago
There is a newer version of this series
include/linux/alloc_tag.h | 2 +-
lib/alloc_tag.c           | 7 +++++++
2 files changed, 8 insertions(+), 1 deletion(-)
[PATCH v2] mm/codetag: clear tags before swap
Posted by David Wang 1 year ago 
When CONFIG_MEM_ALLOC_PROFILING_DEBUG is set, kernel WARN would be
triggered when calling __alloc_tag_ref_set() during swap:

	alloc_tag was not cleared (got tag for mm/filemap.c:1951)
	WARNING: CPU: 0 PID: 816 at ./include/linux/alloc_tag.h...

Clear code tags before swap can fix the warning. And this patch also fix
a potential invalid address dereference in alloc_tag_add_check() when
CONFIG_MEM_ALLOC_PROFILING_DEBUG is set and ref->ct is CODETAG_EMPTY,
which is defined as ((void *)1).

Signed-off-by: David Wang <00107082@163.com>
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202412112227.df61ebb-lkp@intel.com
Suggested-by: Suren Baghdasaryan <surenb@google.com>
---
 include/linux/alloc_tag.h | 2 +-
 lib/alloc_tag.c           | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h
index 7c0786bdf9af..cba024bf2db3 100644
--- a/include/linux/alloc_tag.h
+++ b/include/linux/alloc_tag.h
@@ -135,7 +135,7 @@ static inline struct alloc_tag_counters alloc_tag_read(struct alloc_tag *tag)
 #ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG
 static inline void alloc_tag_add_check(union codetag_ref *ref, struct alloc_tag *tag)
 {
-	WARN_ONCE(ref && ref->ct,
+	WARN_ONCE(ref && ref->ct && !is_codetag_empty(ref),
 		  "alloc_tag was not cleared (got tag for %s:%u)\n",
 		  ref->ct->filename, ref->ct->lineno);
 
diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
index 35f7560a309a..3a0413462e9f 100644
--- a/lib/alloc_tag.c
+++ b/lib/alloc_tag.c
@@ -209,6 +209,13 @@ void pgalloc_tag_swap(struct folio *new, struct folio *old)
 		return;
 	}
 
+	/*
+	 * Clear tag references to avoid debug warning when using
+	 * __alloc_tag_ref_set() with non-empty reference.
+	 */
+	set_codetag_empty(&ref_old);
+	set_codetag_empty(&ref_new);
+
 	/* swap tags */
 	__alloc_tag_ref_set(&ref_old, tag_new);
 	update_page_tag_ref(handle_old, &ref_old);
-- 
2.39.2
Re: [PATCH v2] mm/codetag: clear tags before swap
Posted by Suren Baghdasaryan 1 year ago 
On Thu, Dec 12, 2024 at 12:29 AM David Wang <00107082@163.com> wrote:
>
> When CONFIG_MEM_ALLOC_PROFILING_DEBUG is set, kernel WARN would be
> triggered when calling __alloc_tag_ref_set() during swap:
>
>         alloc_tag was not cleared (got tag for mm/filemap.c:1951)
>         WARNING: CPU: 0 PID: 816 at ./include/linux/alloc_tag.h...
>
> Clear code tags before swap can fix the warning. And this patch also fix
> a potential invalid address dereference in alloc_tag_add_check() when
> CONFIG_MEM_ALLOC_PROFILING_DEBUG is set and ref->ct is CODETAG_EMPTY,
> which is defined as ((void *)1).
>
> Signed-off-by: David Wang <00107082@163.com>
> Reported-by: kernel test robot <oliver.sang@intel.com>
> Closes: https://lore.kernel.org/oe-lkp/202412112227.df61ebb-lkp@intel.com
> Suggested-by: Suren Baghdasaryan <surenb@google.com>

I didn't really suggest much in this patch, so please replace above
Suggested-by with:

Acked-by: Suren Baghdasaryan <surenb@google.com>

Thanks for fixing this!

> ---
>  include/linux/alloc_tag.h | 2 +-
>  lib/alloc_tag.c           | 7 +++++++
>  2 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h
> index 7c0786bdf9af..cba024bf2db3 100644
> --- a/include/linux/alloc_tag.h
> +++ b/include/linux/alloc_tag.h
> @@ -135,7 +135,7 @@ static inline struct alloc_tag_counters alloc_tag_read(struct alloc_tag *tag)
>  #ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG
>  static inline void alloc_tag_add_check(union codetag_ref *ref, struct alloc_tag *tag)
>  {
> -       WARN_ONCE(ref && ref->ct,
> +       WARN_ONCE(ref && ref->ct && !is_codetag_empty(ref),
>                   "alloc_tag was not cleared (got tag for %s:%u)\n",
>                   ref->ct->filename, ref->ct->lineno);
>
> diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
> index 35f7560a309a..3a0413462e9f 100644
> --- a/lib/alloc_tag.c
> +++ b/lib/alloc_tag.c
> @@ -209,6 +209,13 @@ void pgalloc_tag_swap(struct folio *new, struct folio *old)
>                 return;
>         }
>
> +       /*
> +        * Clear tag references to avoid debug warning when using
> +        * __alloc_tag_ref_set() with non-empty reference.
> +        */
> +       set_codetag_empty(&ref_old);
> +       set_codetag_empty(&ref_new);
> +
>         /* swap tags */
>         __alloc_tag_ref_set(&ref_old, tag_new);
>         update_page_tag_ref(handle_old, &ref_old);
> --
> 2.39.2
>
[PATCH v3] mm/codetag: clear tags before swap
Posted by David Wang 1 year ago 
When CONFIG_MEM_ALLOC_PROFILING_DEBUG is set, kernel WARN would be
triggered when calling __alloc_tag_ref_set() during swap:

	alloc_tag was not cleared (got tag for mm/filemap.c:1951)
	WARNING: CPU: 0 PID: 816 at ./include/linux/alloc_tag.h...

Clear code tags before swap can fix the warning. And this patch also fix
a potential invalid address dereference in alloc_tag_add_check() when
CONFIG_MEM_ALLOC_PROFILING_DEBUG is set and ref->ct is CODETAG_EMPTY,
which is defined as ((void *)1).

Signed-off-by: David Wang <00107082@163.com>
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202412112227.df61ebb-lkp@intel.com
Acked-by: Suren Baghdasaryan <surenb@google.com>
---
 include/linux/alloc_tag.h | 2 +-
 lib/alloc_tag.c           | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h
index 7c0786bdf9af..cba024bf2db3 100644
--- a/include/linux/alloc_tag.h
+++ b/include/linux/alloc_tag.h
@@ -135,7 +135,7 @@ static inline struct alloc_tag_counters alloc_tag_read(struct alloc_tag *tag)
 #ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG
 static inline void alloc_tag_add_check(union codetag_ref *ref, struct alloc_tag *tag)
 {
-	WARN_ONCE(ref && ref->ct,
+	WARN_ONCE(ref && ref->ct && !is_codetag_empty(ref),
 		  "alloc_tag was not cleared (got tag for %s:%u)\n",
 		  ref->ct->filename, ref->ct->lineno);
 
diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
index 35f7560a309a..3a0413462e9f 100644
--- a/lib/alloc_tag.c
+++ b/lib/alloc_tag.c
@@ -209,6 +209,13 @@ void pgalloc_tag_swap(struct folio *new, struct folio *old)
 		return;
 	}
 
+	/*
+	 * Clear tag references to avoid debug warning when using
+	 * __alloc_tag_ref_set() with non-empty reference.
+	 */
+	set_codetag_empty(&ref_old);
+	set_codetag_empty(&ref_new);
+
 	/* swap tags */
 	__alloc_tag_ref_set(&ref_old, tag_new);
 	update_page_tag_ref(handle_old, &ref_old);
-- 
2.39.2
Re: [PATCH v3] mm/codetag: clear tags before swap
Posted by Andrew Morton 1 year ago 
On Fri, 13 Dec 2024 09:33:32 +0800 David Wang <00107082@163.com> wrote:

> When CONFIG_MEM_ALLOC_PROFILING_DEBUG is set, kernel WARN would be
> triggered when calling __alloc_tag_ref_set() during swap:
> 
> 	alloc_tag was not cleared (got tag for mm/filemap.c:1951)
> 	WARNING: CPU: 0 PID: 816 at ./include/linux/alloc_tag.h...
> 
> Clear code tags before swap can fix the warning. And this patch also fix
> a potential invalid address dereference in alloc_tag_add_check() when
> CONFIG_MEM_ALLOC_PROFILING_DEBUG is set and ref->ct is CODETAG_EMPTY,
> which is defined as ((void *)1).
> 
> Signed-off-by: David Wang <00107082@163.com>
> Reported-by: kernel test robot <oliver.sang@intel.com>
> Closes: https://lore.kernel.org/oe-lkp/202412112227.df61ebb-lkp@intel.com

This points at 

51f43d5d82ed ("mm/codetag: swap tags when migrate pages"), which had
	Fixes: e0a955bf7f61 ("mm/codetag: add pgalloc_tag_copy()")

e0a955bf7f61 ("mm/codetag: add pgalloc_tag_copy()") had
	Fixes: dcfe378c81f7 ("lib: introduce support for page allocation tagging")
	Cc: <stable@vger.kernel.org>

And I'm thinking that this fix should have
	Fixes: 51f43d5d82ed ("mm/codetag: swap tags when migrate pages")
	Cc: <stable@vger.kernel.org>
Re: [PATCH v3] mm/codetag: clear tags before swap
Posted by Suren Baghdasaryan 1 year ago 
On Thu, Dec 12, 2024 at 8:12 PM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Fri, 13 Dec 2024 09:33:32 +0800 David Wang <00107082@163.com> wrote:
>
> > When CONFIG_MEM_ALLOC_PROFILING_DEBUG is set, kernel WARN would be
> > triggered when calling __alloc_tag_ref_set() during swap:
> >
> >       alloc_tag was not cleared (got tag for mm/filemap.c:1951)
> >       WARNING: CPU: 0 PID: 816 at ./include/linux/alloc_tag.h...
> >
> > Clear code tags before swap can fix the warning. And this patch also fix
> > a potential invalid address dereference in alloc_tag_add_check() when
> > CONFIG_MEM_ALLOC_PROFILING_DEBUG is set and ref->ct is CODETAG_EMPTY,
> > which is defined as ((void *)1).
> >
> > Signed-off-by: David Wang <00107082@163.com>
> > Reported-by: kernel test robot <oliver.sang@intel.com>
> > Closes: https://lore.kernel.org/oe-lkp/202412112227.df61ebb-lkp@intel.com
>
> This points at
>
> 51f43d5d82ed ("mm/codetag: swap tags when migrate pages"), which had
>         Fixes: e0a955bf7f61 ("mm/codetag: add pgalloc_tag_copy()")
>
> e0a955bf7f61 ("mm/codetag: add pgalloc_tag_copy()") had
>         Fixes: dcfe378c81f7 ("lib: introduce support for page allocation tagging")
>         Cc: <stable@vger.kernel.org>
>
> And I'm thinking that this fix should have
>         Fixes: 51f43d5d82ed ("mm/codetag: swap tags when migrate pages")
>         Cc: <stable@vger.kernel.org>

Yes, that is correct. Sorry for missing that.

>

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