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Subject[PATCH AUTOSEL 5.2 50/85] mm/z3fold: don't try to use buddy slots after free
Date
From: Vitaly Wool <vitalywool@gmail.com>

[ Upstream commit bb9a374dfa3a2f46581455ab66cd1d24c5e3d183 ]

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: 7c2b8baa61fe ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
mm/z3fold.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/z3fold.c b/mm/z3fold.c
index 985732c8b025..e1686bf6d689 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -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)
--
2.20.1
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