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mm/z3fold: don't try to use buddy slots after free 

As reported by Henry Burns:

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*

To fix this, add pointer to the pool back to z3fold_header and modify
zhdr_to_pool to return zhdr->pool.

Link: http://lkml.kernel.org/r/20190708134808.e89f3bfadd9f6ffd7eff9ba9@gmail.com
Fixes: 7c2b8baa61  ("mm/z3fold.c: add structure for buddy handles")
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reported-by: Henry Burns <henryburns@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Jonathan Adams <jwadams@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Vitaly Wool 2019-07-16 16:25:48 -07:00 committed by Linus Torvalds
parent 5095062641
commit bb9a374dfa
1 changed files with 4 additions and 1 deletions
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5
mm/z3fold.c
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@ -101,6 +101,7 @@ struct z3fold_buddy_slots {
* @refcount: reference count for the z3fold page
* @work: work_struct for page layout optimization
* @slots: pointer to the structure holding buddy slots
* @pool: pointer to the containing pool
* @cpu: CPU which this page "belongs" to
* @first_chunks: the size of the first buddy in chunks, 0 if free
* @middle_chunks: the size of the middle buddy in chunks, 0 if free
@ -114,6 +115,7 @@ struct z3fold_header {
struct kref refcount;
struct work_struct work;
struct z3fold_buddy_slots *slots;
struct z3fold_pool *pool;
short cpu;
unsigned short first_chunks;
unsigned short middle_chunks;
@ -320,6 +322,7 @@ static struct z3fold_header *init_z3fold_page(struct page *page,
zhdr->start_middle = 0;
zhdr->cpu = -1;
zhdr->slots = slots;
zhdr->pool = pool;
INIT_LIST_HEAD(&zhdr->buddy);
INIT_WORK(&zhdr->work, compact_page_work);
return zhdr;
@ -426,7 +429,7 @@ static enum buddy handle_to_buddy(unsigned long handle)
static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr)
{
return slots_to_pool(zhdr->slots);
return zhdr->pool;
}
static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)