The patch titled
Subject: mm/z3fold.c: fix z3fold_buddy_slots use after free
has been added to the -mm tree. Its filename is
mm-z3fold-fix-z3fold_buddy_slots-use-after-free.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-z3fold-fix-z3fold_buddy_slots-use-after-free.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-z3fold-fix-z3fold_buddy_slots-use-after-free.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
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------------------------------------------------------
From: Henry Burns <henryburns@xxxxxxxxxx>
Subject: mm/z3fold.c: fix z3fold_buddy_slots use after free
Running z3fold stress testing with address sanitization showed zhdr->slots
was being used after it was freed.
z3fold_free(z3fold_pool, handle)
free_handle(handle)
kmem_cache_free(pool->c_handle, zhdr->slots)
release_z3fold_page_locked_list(kref)
__release_z3fold_page(zhdr, true)
zhdr_to_pool(zhdr)
slots_to_pool(zhdr->slots) *BOOM*
Instead we split free_handle into two functions, release_handle() and
free_slots(). We use release_handle() in place of free_handle(), and use
free_slots() to call kmem_cache_free() after __release_z3fold_page() is
done.
Link: http://lkml.kernel.org/r/20190701173042.221453-1-henryburns@xxxxxxxxxx
Fixes: 7c2b8baa61fe ("mm/z3fold.c: add structure for buddy handles")
Signed-off-by: Henry Burns <henryburns@xxxxxxxxxx>
Cc: Vitaly Wool <vitalywool@xxxxxxxxx>
Cc: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
Cc: Vitaly Vul <vitaly.vul@xxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
Cc: Xidong Wang <wangxidong_97@xxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Jonathan Adams <jwadams@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/z3fold.c | 33 ++++++++++++++-------------------
1 file changed, 14 insertions(+), 19 deletions(-)
--- a/mm/z3fold.c~mm-z3fold-fix-z3fold_buddy_slots-use-after-free
+++ a/mm/z3fold.c
@@ -214,31 +214,24 @@ static inline struct z3fold_buddy_slots
return (struct z3fold_buddy_slots *)(handle & ~(SLOTS_ALIGN - 1));
}
-static inline void free_handle(unsigned long handle)
+static inline void release_handle(unsigned long handle)
{
- struct z3fold_buddy_slots *slots;
- int i;
- bool is_free;
-
if (handle & (1 << PAGE_HEADLESS))
return;
WARN_ON(*(unsigned long *)handle == 0);
*(unsigned long *)handle = 0;
- slots = handle_to_slots(handle);
- is_free = true;
- for (i = 0; i <= BUDDY_MASK; i++) {
- if (slots->slot[i]) {
- is_free = false;
- break;
- }
- }
+}
- if (is_free) {
- struct z3fold_pool *pool = slots_to_pool(slots);
+/* At this point all of the slots should be empty */
+static inline void free_slots(struct z3fold_buddy_slots *slots)
+{
+ struct z3fold_pool *pool = slots_to_pool(slots);
+ int i;
- kmem_cache_free(pool->c_handle, slots);
- }
+ for (i = 0; i <= BUDDY_MASK; i++)
+ VM_BUG_ON(slots->slot[i]);
+ kmem_cache_free(pool->c_handle, slots);
}
static struct dentry *z3fold_do_mount(struct file_system_type *fs_type,
@@ -432,7 +425,8 @@ static inline struct z3fold_pool *zhdr_t
static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
{
struct page *page = virt_to_page(zhdr);
- struct z3fold_pool *pool = zhdr_to_pool(zhdr);
+ struct z3fold_buddy_slots *slots = zhdr->slots;
+ struct z3fold_pool *pool = slots_to_pool(slots);
WARN_ON(!list_empty(&zhdr->buddy));
set_bit(PAGE_STALE, &page->private);
@@ -443,6 +437,7 @@ static void __release_z3fold_page(struct
spin_unlock(&pool->lock);
if (locked)
z3fold_page_unlock(zhdr);
+ free_slots(slots);
spin_lock(&pool->stale_lock);
list_add(&zhdr->buddy, &pool->stale);
queue_work(pool->release_wq, &pool->work);
@@ -1010,7 +1005,7 @@ static void z3fold_free(struct z3fold_po
return;
}
- free_handle(handle);
+ release_handle(handle);
if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) {
atomic64_dec(&pool->pages_nr);
return;
_
Patches currently in -mm which might be from henryburns@xxxxxxxxxx are
mm-z3fold-fix-z3fold_buddy_slots-use-after-free.patch
