[v3,33/35] codetag: debug: mark codetags for reserved pages as empty

Commit Message

Suren Baghdasaryan Feb. 12, 2024, 9:39 p.m. UTC

To avoid debug warnings while freeing reserved pages which were not
allocated with usual allocators, mark their codetags as empty before
freeing.

Signed-off-by: Suren Baghdasaryan <[e-mail]>
---
 include/linux/alloc_tag.h   | 2 ++
 include/linux/mm.h          | 8 ++++++++
 include/linux/pgalloc_tag.h | 2 ++
 mm/mm_init.c                | 9 +++++++++
 4 files changed, 21 insertions(+)

Comments

Kees Cook Feb. 12, 2024, 10:45 p.m. UTC | #1

On Mon, Feb 12, 2024 at 01:39:19PM -0800, Suren Baghdasaryan wrote:
> To avoid debug warnings while freeing reserved pages which were not
> allocated with usual allocators, mark their codetags as empty before
> freeing.

How do these get their codetags to begin with? Regardless:

Reviewed-by: Kees Cook <[e-mail]>

Suren Baghdasaryan Feb. 13, 2024, 12:15 a.m. UTC | #2

On Mon, Feb 12, 2024 at 2:45 PM Kees Cook <[e-mail]> wrote:
>
> On Mon, Feb 12, 2024 at 01:39:19PM -0800, Suren Baghdasaryan wrote:
> > To avoid debug warnings while freeing reserved pages which were not
> > allocated with usual allocators, mark their codetags as empty before
> > freeing.
>
> How do these get their codetags to begin with?

The space for the codetag reference is inside the page_ext and that
reference is set to NULL. So, unless we set the reference as empty
(set it to CODETAG_EMPTY), the free routine will detect that we are
freeing an allocation that has never been accounted for and will issue
a warning. To prevent this warning we use this CODETAG_EMPTY to denote
that this codetag reference is expected to be empty because it was not
allocated in a usual way.

> Regardless:
>
> Reviewed-by: Kees Cook <[e-mail]>
>
> --
> Kees Cook

Patch

diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h
index 1f3207097b03..102caf62c2a9 100644
--- a/include/linux/alloc_tag.h
+++ b/include/linux/alloc_tag.h
@@ -95,6 +95,7 @@  static inline void set_codetag_empty(union codetag_ref *ref)
 #else /* CONFIG_MEM_ALLOC_PROFILING_DEBUG */
 
 static inline bool is_codetag_empty(union codetag_ref *ref) { return false; }
+static inline void set_codetag_empty(union codetag_ref *ref) {}
 
 #endif /* CONFIG_MEM_ALLOC_PROFILING_DEBUG */
 
@@ -155,6 +156,7 @@  static inline void alloc_tag_sub(union codetag_ref *ref, size_t bytes) {}
 static inline void alloc_tag_sub_noalloc(union codetag_ref *ref, size_t bytes) {}
 static inline void alloc_tag_add(union codetag_ref *ref, struct alloc_tag *tag,
 				 size_t bytes) {}
+static inline void set_codetag_empty(union codetag_ref *ref) {}
 
 #endif
 
diff --git a/include/linux/mm.h b/include/linux/mm.h
index f5a97dec5169..ac1b661987ed 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -5,6 +5,7 @@ 
 #include <linux/errno.h>
 #include <linux/mmdebug.h>
 #include <linux/gfp.h>
+#include <linux/pgalloc_tag.h>
 #include <linux/bug.h>
 #include <linux/list.h>
 #include <linux/mmzone.h>
@@ -3112,6 +3113,13 @@  extern void reserve_bootmem_region(phys_addr_t start,
 /* Free the reserved page into the buddy system, so it gets managed. */
 static inline void free_reserved_page(struct page *page)
 {
+	union codetag_ref *ref;
+
+	ref = get_page_tag_ref(page);
+	if (ref) {
+		set_codetag_empty(ref);
+		put_page_tag_ref(ref);
+	}
 	ClearPageReserved(page);
 	init_page_count(page);
 	__free_page(page);
diff --git a/include/linux/pgalloc_tag.h b/include/linux/pgalloc_tag.h
index 0174aff5e871..ae9b0f359264 100644
--- a/include/linux/pgalloc_tag.h
+++ b/include/linux/pgalloc_tag.h
@@ -93,6 +93,8 @@  static inline void pgalloc_tag_split(struct page *page, unsigned int nr)
 
 #else /* CONFIG_MEM_ALLOC_PROFILING */
 
+static inline union codetag_ref *get_page_tag_ref(struct page *page) { return NULL; }
+static inline void put_page_tag_ref(union codetag_ref *ref) {}
 static inline void pgalloc_tag_add(struct page *page, struct task_struct *task,
 				   unsigned int order) {}
 static inline void pgalloc_tag_sub(struct page *page, unsigned int order) {}
diff --git a/mm/mm_init.c b/mm/mm_init.c
index e9ea2919d02d..f5386632fe86 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -2566,6 +2566,7 @@  void __init set_dma_reserve(unsigned long new_dma_reserve)
 void __init memblock_free_pages(struct page *page, unsigned long pfn,
 							unsigned int order)
 {
+	union codetag_ref *ref;
 
 	if (IS_ENABLED(CONFIG_DEFERRED_STRUCT_PAGE_INIT)) {
 		int nid = early_pfn_to_nid(pfn);
@@ -2578,6 +2579,14 @@  void __init memblock_free_pages(struct page *page, unsigned long pfn,
 		/* KMSAN will take care of these pages. */
 		return;
 	}
+
+	/* pages were reserved and not allocated */
+	ref = get_page_tag_ref(page);
+	if (ref) {
+		set_codetag_empty(ref);
+		put_page_tag_ref(ref);
+	}
+
 	__free_pages_core(page, order);
 }